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data-v-30c06bd3><!--[--><p class="text" data-v-b05232f3>1-1: Numbers</p><!--]--><!----></a><!----></div><!----></div><div class="VPSidebarItem level-1" data-v-b05232f3 data-v-b05232f3><!----><!----></div><div class="VPSidebarItem level-1" data-v-b05232f3 data-v-b05232f3><!----><!----></div><div class="VPSidebarItem level-1" data-v-b05232f3 data-v-b05232f3><!----><!----></div><div class="VPSidebarItem level-1" data-v-b05232f3 data-v-b05232f3><!----><!----></div><!--]--></div></section></div><!--]--><!--[--><!--]--></nav></aside><div class="VPContent has-sidebar" id="VPContent" data-v-93a960b4 data-v-0bd490fb><div class="VPDoc has-sidebar has-aside" data-v-0bd490fb data-v-c5936a1e><div class="container" data-v-c5936a1e><div class="aside" data-v-c5936a1e><div class="aside-curtain" data-v-c5936a1e></div><div class="aside-container" data-v-c5936a1e><div class="aside-content" data-v-c5936a1e><div class="VPDocAside" data-v-c5936a1e data-v-cdc66372><!--[--><!--]--><!--[--><!--]--><div class="VPDocAsideOutline" data-v-cdc66372 data-v-5dd9d5f6><div class="content" data-v-5dd9d5f6><div class="outline-marker" data-v-5dd9d5f6></div><div class="outline-title" data-v-5dd9d5f6>TOC</div><nav aria-labelledby="doc-outline-aria-label" data-v-5dd9d5f6><span class="visually-hidden" id="doc-outline-aria-label" data-v-5dd9d5f6> Table of Contents for current page </span><ul class="root" data-v-5dd9d5f6 data-v-1188541a><!--[--><!--]--></ul></nav></div></div><!--[--><!--]--><div class="spacer" data-v-cdc66372></div><!--[--><!--]--><!----><!--[--><!--]--><!--[--><!--[--><!--[--><!--[--><div class="VPDocAsideSponsors"><div class="VPSponsors vp-sponsor aside"><!--[--><section class="vp-sponsor-section"><!----><div class="VPSponsorsGrid vp-sponsor-grid medium"><!--[--><div class="vp-sponsor-grid-item"><a class="vp-sponsor-grid-link" target="_blank" rel="sponsored noopener"><article class="vp-sponsor-grid-box"><h4 class="visually-hidden"></h4><img class="vp-sponsor-grid-image" src="https://cdn.jsdelivr.net/gh/maomao1996/picture/sponsor/wechat-color.jpg"></article></a></div><!--]--></div></section><section class="vp-sponsor-section"><!----><div class="VPSponsorsGrid vp-sponsor-grid medium"><!--[--><div class="vp-sponsor-grid-item"><a class="vp-sponsor-grid-link" target="_blank" rel="sponsored noopener"><article class="vp-sponsor-grid-box"><h4 class="visually-hidden"></h4><img class="vp-sponsor-grid-image" src="https://cdn.jsdelivr.net/gh/maomao1996/picture/sponsor/alipay-color.jpg"></article></a></div><!--]--></div></section><!--]--></div></div><!--]--><!--]--><!--]--><!--]--></div></div></div></div><div class="content" data-v-c5936a1e><div class="content-container" data-v-c5936a1e><!--[--><!--]--><main class="main" data-v-c5936a1e><div style="position:relative;" class="vp-doc _javascript_notes_1_1-1" data-v-c5936a1e><div><h1 id="_1-1-values" tabindex="-1">1-1: Values <a class="header-anchor" href="#_1-1-values" aria-hidden="true">#</a></h1><h2 id="_1-1-1-numbers" tabindex="-1">1-1-1: Numbers <span class="VPBadge danger" data-v-350d3852><!--[-->must know<!--]--></span> <a class="header-anchor" href="#_1-1-1-numbers" aria-hidden="true">#</a></h2><p>Values of the <em>number</em> type are numeric values, normally written as follows,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#F78C6C;">144</span></span>
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<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#D19A66;">144</span></span>
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<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><ul><li><p>Put this into a program, it will cause the number 144 to come into existence inside the computer, with the following bash script, 144 might looks like this in bits,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#F78C6C;">0100000001100010000000000000000000000000000000000000000000000000</span></span>
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<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#D19A66;">0100000001100010000000000000000000000000000000000000000000000000</span></span>
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<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div></li><li><p>With the following bash script, 144 will be converted into binary values in integer form,</p><div class="language-sh line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">sh</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#A6ACCD;">ip1</span><span style="color:#89DDFF;">=</span><span style="color:#F78C6C;">144</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;"># defines a variable named ip1, with the value of 10</span></span>
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<span class="line"><span style="color:#82AAFF;">echo</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">"</span><span style="color:#C3E88D;">obase=2;</span><span style="color:#A6ACCD;">$ip1</span><span style="color:#89DDFF;">"</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">|</span><span style="color:#A6ACCD;"> </span><span style="color:#FFCB6B;">bc</span><span style="color:#A6ACCD;"> </span><span style="color:#676E95;font-style:italic;"># convert the value to binary via bc</span></span>
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<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#E06C75;">ip1</span><span style="color:#56B6C2;">=</span><span style="color:#D19A66;">144</span><span style="color:#ABB2BF;"> </span><span style="color:#7F848E;font-style:italic;"># defines a variable named ip1, with the value of 10</span></span>
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<span class="line"><span style="color:#56B6C2;">echo</span><span style="color:#ABB2BF;"> </span><span style="color:#98C379;">"obase=2;</span><span style="color:#E06C75;">$ip1</span><span style="color:#98C379;">"</span><span style="color:#ABB2BF;"> | bc </span><span style="color:#7F848E;font-style:italic;"># convert the value to binary via bc</span></span>
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<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><ul><li>The variable <code>ip1</code> is assigned the value 144.</li><li>The <code>echo</code> command prints out the string "obase=2;144", where "obase=2;" is an argument for <code>bc</code> that tells it to output the result in base 2 (binary), and "10" is the decimal number we want to convert.</li><li>The output of the <code>echo</code> command is piped (using the <code>|</code> character) to <code>bc</code>, which takes the input "<code>obase=2;144</code>" and interprets it as a command to convert the number 10 to binary.</li><li>Finally, the binary equivalent of 144, which is "10010000", is printed to the terminal.</li></ul></li></ul><div class="tip custom-block"><p class="custom-block-title">TIP</p><p>But the standard describes JavaScript numbers as 64-bit floating-point values, which indicates fractions and exponents are available.</p></div><p>Not all whole numbers <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>1</mn><msup><mn>0</mn><mn>19</mn></msup></mrow><annotation encoding="application/x-tex">10^{19}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord">1</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">19</span></span></span></span></span></span></span></span></span></span></span></span> fit in a JavaScript number. There are also negative numbers, so one of the bits has to be used to store the sign of the number.</p><ul><li>11 bits are used to store the position of the decimal dot within the number.</li><li>52 bits, any whole number less than <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mn>2</mn><mn>52</mn></msup></mrow><annotation encoding="application/x-tex">2^{52}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord"><span class="mord">2</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">52</span></span></span></span></span></span></span></span></span></span></span></span>, which is more than <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>1</mn><msup><mn>0</mn><mn>15</mn></msup></mrow><annotation encoding="application/x-tex">10^{15}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord">1</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">15</span></span></span></span></span></span></span></span></span></span></span></span> will safely fit in a JavaScript number, numbers we are using stay well below that.</li></ul><p>Fractional numbers are written by using a dot,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#F78C6C;">9.81</span></span>
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<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#D19A66;">9.81</span></span>
|
||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>For extreme huge or tiny numbers, we can also use "scientific" notion by adding an <code>e</code>, followed by the exponent of the number,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#F78C6C;">2.998e8</span></span>
|
||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#D19A66;">2.998e8</span></span>
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||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>This indicates <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mn>2.998</mn><mo>×</mo><mn>1</mn><msup><mn>0</mn><mn>8</mn></msup><mo>=</mo><mn>29980000</mn></mrow><annotation encoding="application/x-tex">2.998 \times 10^8 = 29980000</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7278em;vertical-align:-0.0833em;"></span><span class="mord">2.998</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord">1</span><span class="mord"><span class="mord">0</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight">8</span></span></span></span></span></span></span></span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6444em;"></span><span class="mord">29980000</span></span></span></span>.</p><p>Calculations with whole numbers (referred as <em>integers</em>) that fits into 52 bits are guaranteed to be always precise, but calculation with fraction numbers are generally not.</p><ul><li>Such as <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>π</mi></mrow><annotation encoding="application/x-tex">\pi</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">π</span></span></span></span> cannot be precisely expressed by a finite amount of decimal digits, <strong>thus many numbers lose some precision when only 64 bits are available to store them.</strong></li></ul><details class="details custom-block"><summary>1-1-1: Numbers review</summary><ul><li>64 bits: A 64-bit number is a binary sequence of 64 bits, which can represent <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mn>2</mn><mn>64</mn></msup></mrow><annotation encoding="application/x-tex">2^{64}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord"><span class="mord">2</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">64</span></span></span></span></span></span></span></span></span></span></span></span> (18,446,744,073,709,551,616) different values. This is commonly used for representing memory addresses and integers with large values in computer systems.</li><li>11 bits: An 11-bit number is a binary sequence of 11 bits, which can represent <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mn>2</mn><mn>11</mn></msup></mrow><annotation encoding="application/x-tex">2^{11}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord"><span class="mord">2</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">11</span></span></span></span></span></span></span></span></span></span></span></span> (2,048) different values. This is often used in computer systems for encoding small integers, such as color values in images.</li><li>52 bits: A 52-bit number is a binary sequence of 52 bits, which can represent <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msup><mn>2</mn><mn>52</mn></msup></mrow><annotation encoding="application/x-tex">2^{52}</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8141em;"></span><span class="mord"><span class="mord">2</span><span class="msupsub"><span class="vlist-t"><span class="vlist-r"><span class="vlist" style="height:0.8141em;"><span style="top:-3.063em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mtight"><span class="mord mtight">52</span></span></span></span></span></span></span></span></span></span></span></span> (4,503,599,627,370,496) different values. This is often used for representing the significand or mantissa portion of a floating-point number in computer systems.</li></ul></details><h2 id="_1-1-2-arithmetic" tabindex="-1">1-1-2: Arithmetic <a class="header-anchor" href="#_1-1-2-arithmetic" aria-hidden="true">#</a></h2><p>The main thing to do with numbers is arithmetic. Arithmetic operations such as addition or multiplication take two number values and produce a new number from them, the following is an example of calculation in JavaScript.</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#F78C6C;">100</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">4</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">*</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">11</span></span>
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<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#D19A66;">100</span><span style="color:#ABB2BF;"> </span><span style="color:#56B6C2;">+</span><span style="color:#ABB2BF;"> </span><span style="color:#D19A66;">4</span><span style="color:#ABB2BF;"> </span><span style="color:#56B6C2;">*</span><span style="color:#ABB2BF;"> </span><span style="color:#D19A66;">11</span></span>
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<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><ul><li><p>The <code>+</code> and <code>*</code> symbols are called <em>operators</em>.</p><ul><li><code>+</code> apparently stands for addition while <code>*</code> stands for multiplication.</li></ul></li><li><p>This expression indicates the multiplication takes place first then the adding of 100 comes next as a regard to <a href="https://www.khanacademy.org/math/cc-sixth-grade-math/x0267d782:cc-6th-exponents-and-order-of-operations/cc-6th-order-of-operations/v/more-complicated-order-of-operations-example#:~:text=The%20order%20of%20operations%20is,(from%20left%20to%20right)." target="_blank" rel="noreferrer">PEMDAS</a> rules (Order of Operations).</p></li></ul><p>But we can still overwrite the steps of operation using a parenthesis around the addition,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">;</span><span style="color:#A6ACCD;">(</span><span style="color:#F78C6C;">100</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">4</span><span style="color:#A6ACCD;">) </span><span style="color:#89DDFF;">*</span><span style="color:#A6ACCD;"> </span><span style="color:#F78C6C;">11</span></span>
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||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#ABB2BF;">;(</span><span style="color:#D19A66;">100</span><span style="color:#ABB2BF;"> </span><span style="color:#56B6C2;">+</span><span style="color:#ABB2BF;"> </span><span style="color:#D19A66;">4</span><span style="color:#ABB2BF;">) </span><span style="color:#56B6C2;">*</span><span style="color:#ABB2BF;"> </span><span style="color:#D19A66;">11</span></span>
|
||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>For subtraction, there is the <code>-</code> operator, and division can be done with <code>/</code>. When operators appear together without parentheses, they are applied is determined by the <em>precedence</em> of the operators.</p><ul><li>When multiple operators with the same precedence appear next to each other (as <code>1-2+1</code>), they are applied left to right (refers to PEMDAS).</li><li>Precedence: Priorities.</li></ul><div class="warning custom-block"><p class="custom-block-title">WARNING</p><p>When is doubt, don't care about precedence, just add parentheses for order of operation.</p></div><p>There is one more arithmetic operator, which is the <code>%</code> percent sign used to represent the <em>modulo</em> operation. <strong>The term "X modulo Y" is defined as the remainder of dividing X by Y.</strong></p><ul><li>For example, <code>314 % 100</code> is <code>14</code>, <code>10 % 3</code> is <code>1</code>, and <code>144 % 12</code> is 0 because there are no remainders.</li><li>Modulo's precedence is the same as that of multiplication and division.</li></ul><details class="details custom-block"><summary>1-2: Arithmetic review</summary><ul><li>All of the operators in JavaScript follows precedence rules, or referred as PEMDAS in conventional math. <ul><li><code>+</code> and <code>-</code> has the same lowest precedence.</li><li><code>*</code> , <code>/</code> and <code>%</code> has the same medium precedence.</li><li><code>()</code> has the highest precedence, followed on with brackets.</li></ul></li><li>The symbol <code>%</code> refers to "modulo", in mathematical reading, we say "X modulo Y" is the remainder of X over Y.</li></ul></details><h2 id="_1-1-3-strings" tabindex="-1">1-1-3: Strings <a class="header-anchor" href="#_1-1-3-strings" aria-hidden="true">#</a></h2><p>The next data type is the <em>string</em>. Its use is not as evident from its name as with numbers, it also fulfills a very basic role.</p><ul><li>Strings are used to represent text.</li><li>Strings are usually written by enclosing the contents with quotes.</li></ul><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">Lorem ipsum dolor sit amet, consectetur adipiscing elit.</span><span style="color:#89DDFF;">'</span></span>
|
||
<span class="line"><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">Lorem ipsum dolor sit amet, consectetur adipiscing elit.</span><span style="color:#89DDFF;">'</span></span>
|
||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#98C379;">'Lorem ipsum dolor sit amet, consectetur adipiscing elit.'</span></span>
|
||
<span class="line"><span style="color:#98C379;">'Lorem ipsum dolor sit amet, consectetur adipiscing elit.'</span></span>
|
||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><div class="tip custom-block"><p class="custom-block-title">TIP</p><p><strong>Both single and double quotes</strong> can be used to mark strings</p><ul><li>As long as the quotes at the start and the end of the string match.</li></ul></div><p>Almost anything can be put between quotes, and JavaScript will make a string value out of it. But the followings are tricky to be put between quotes.</p><ul><li><strong>Newlines</strong>: The things we get when we press <kbd>enter</kbd> on keyboard. We uses <code>\n</code> to represent.</li><li><strong>New tab</strong>: Similarly like newlines, <code>\t</code> indicates a new tab being indented.</li></ul><p>Take the following string as an example,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">Lorem ipsum dolor sit amet,</span><span style="color:#A6ACCD;">\n</span><span style="color:#C3E88D;"> consectetur adipiscing elit.</span><span style="color:#89DDFF;">'</span></span>
|
||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#98C379;">'Lorem ipsum dolor sit amet,</span><span style="color:#56B6C2;">\n</span><span style="color:#98C379;"> consectetur adipiscing elit.'</span></span>
|
||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>The following will be the rendered output,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#A6ACCD;">Lorem ipsum dolor sit amet</span><span style="color:#89DDFF;">,</span></span>
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||
<span class="line"><span style="color:#A6ACCD;">consectetur adipiscing elit</span><span style="color:#89DDFF;">.</span></span>
|
||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#E06C75;">Lorem</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">ipsum</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">dolor</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">sit</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">amet</span><span style="color:#ABB2BF;">,</span></span>
|
||
<span class="line"><span style="color:#E06C75;">consectetur</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">adipiscing</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">elit</span><span style="color:#ABB2BF;">.</span></span>
|
||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><div class="warning custom-block"><p class="custom-block-title">WARNING</p><p>But the situations where we want a backslash in a string to just be a backslash instead of a special code. By using <code>\\</code> would render the "just slash" to <code>\</code> on output, instead of a special character, as follows,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">"</span><span style="color:#C3E88D;">A newline character is written like </span><span style="color:#A6ACCD;">\"\\</span><span style="color:#C3E88D;">n</span><span style="color:#A6ACCD;">\"</span><span style="color:#C3E88D;">.</span><span style="color:#89DDFF;">"</span></span>
|
||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#98C379;">"A newline character is written like </span><span style="color:#56B6C2;">\"\\</span><span style="color:#98C379;">n</span><span style="color:#56B6C2;">\"</span><span style="color:#98C379;">."</span></span>
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||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div></div><p>Strings cannot be divided, multiplied, or subtracted, unlike integers. But the <code>+</code> operator can be used on the. It concatenates (glues) the two strings together, the following example will produce the string "<code>concatenate</code>".</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">con</span><span style="color:#89DDFF;">'</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">cat</span><span style="color:#89DDFF;">'</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">e</span><span style="color:#89DDFF;">'</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">+</span><span style="color:#A6ACCD;"> </span><span style="color:#89DDFF;">'</span><span style="color:#C3E88D;">nate</span><span style="color:#89DDFF;">'</span></span>
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||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#98C379;">'con'</span><span style="color:#ABB2BF;"> </span><span style="color:#56B6C2;">+</span><span style="color:#ABB2BF;"> </span><span style="color:#98C379;">'cat'</span><span style="color:#ABB2BF;"> </span><span style="color:#56B6C2;">+</span><span style="color:#ABB2BF;"> </span><span style="color:#98C379;">'e'</span><span style="color:#ABB2BF;"> </span><span style="color:#56B6C2;">+</span><span style="color:#ABB2BF;"> </span><span style="color:#98C379;">'nate'</span></span>
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||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><details class="details custom-block"><summary>1-1-3: Strings review</summary><ul><li>Nearly everything could be put into strings in JavaScript</li><li>String could be wrapped with <code>""</code> double quotation marks or <code>''</code> single quotation marks.</li><li>There is a tricky situation in JavaScript's string, where <code>\</code> backslash followed with a character are being introduced specially by the interpreter, such as <code>\n</code> referred as newline, <code>\t</code> referred as new tab. <ul><li><code>\\</code> double backslash will be rendered as a single <code>\</code>.</li><li><code>\&</code> symbols followed after slash will not contain its original function such as connecting, but will be rendered as <code>&</code> on output.</li></ul></li></ul></details><h3 id="_1-1-3-fr-further-reading" tabindex="-1">1-1-3-FR: Further Reading <a class="header-anchor" href="#_1-1-3-fr-further-reading" aria-hidden="true">#</a></h3><p>From the example given in the prior section with a lot of backslashes, it might be hard to understand the concept on at what time the slash will be rendered and when it will be considered as a special character starter.</p><p>The example is given as,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">"</span><span style="color:#C3E88D;">A newline character is written like </span><span style="color:#A6ACCD;">\"\\</span><span style="color:#C3E88D;">n</span><span style="color:#A6ACCD;">\"</span><span style="color:#C3E88D;">.</span><span style="color:#89DDFF;">"</span></span>
|
||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#98C379;">"A newline character is written like </span><span style="color:#56B6C2;">\"\\</span><span style="color:#98C379;">n</span><span style="color:#56B6C2;">\"</span><span style="color:#98C379;">."</span></span>
|
||
<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>The rendered output will be on print,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#A6ACCD;">A newline character is written like </span><span style="color:#89DDFF;">"</span><span style="color:#A6ACCD;">\n</span><span style="color:#89DDFF;">"</span><span style="color:#89DDFF;">.</span></span>
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||
<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#E5C07B;">A</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">newline</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">character</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">is</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">written</span><span style="color:#ABB2BF;"> </span><span style="color:#E06C75;">like</span><span style="color:#ABB2BF;"> </span><span style="color:#98C379;">"</span><span style="color:#56B6C2;">\n</span><span style="color:#98C379;">"</span><span style="color:#ABB2BF;">.</span></span>
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<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>the backslash character (<code>\</code>) is used as an escape character to indicate that the following character(s) should be treated specially. In this case, the <code>"\n"</code> sequence is an escape sequence that represents a newline character. The backslash before the <code>n</code> character tells the JavaScript interpreter that it should treat the <code>n</code> as a special character and not just as the letter "n".</p><p>However, if we want to include an <strong>actual backslash character</strong> (<code>\</code>), we will have to <strong>escape it</strong> by using to two backslashes <code>\\</code>, or else with one single slash the JavaScript interpreter will still determines it as an special operator, Thus <code>\\</code> will print <code>\</code> on output.</p><ul><li><p><strong>But what about the quotation marks used within the quotation marks that wraps the string? Wouldn't JavaScript interpreter throw error?</strong></p><ul><li><p>In the given JavaScript string, the inner set of double quotation marks (<code>"\\n"</code>) is escaped using a backslash (<code>\</code>) character. This tells the JavaScript interpreter to treat the inner double quotation marks as a regular character instead of a string delimiter.</p><p>So when the string is rendered on output, the backslash character will be removed and the inner set of quotation marks will be displayed as a regular character. The rendered string will look like this,</p><div class="language-js line-numbers-mode"><button title="Copy Code" class="copy"></button><span class="lang">js</span><pre class="shiki material-theme-palenight vp-code-dark" tabindex="0"><code><span class="line"><span style="color:#89DDFF;">'</span><span style="color:#A6ACCD;">\n</span><span style="color:#89DDFF;">'</span></span>
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<span class="line"></span></code></pre><pre class="shiki one-dark-pro vp-code-light" tabindex="0"><code><span class="line"><span style="color:#98C379;">'</span><span style="color:#56B6C2;">\n</span><span style="color:#98C379;">'</span></span>
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<span class="line"></span></code></pre><div class="line-numbers-wrapper" aria-hidden="true"><span class="line-number">1</span><br></div></div><p>The outer set of double quotation marks in the original string delimit the entire string and will be displayed as regular quotation marks.</p></li></ul></li></ul><blockquote><p><strong>Source</strong>: ChatGPT CA (Code Analysis)</p></blockquote></div></div></main><!--[--><!--[--><!--[--><!----><!--]--><!--]--><!--]--><footer class="VPDocFooter" data-v-c5936a1e data-v-e033cd21><div class="edit-info" data-v-e033cd21><div class="edit-link" data-v-e033cd21><a class="VPLink link edit-link-button" href="https://github.com/andatoshiki/toshiki-notebook/edit/master/docs/javascript/notes/1/1-1.md" target="_blank" rel="noreferrer" data-v-e033cd21 data-v-30c06bd3><!--[--><svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24" class="edit-link-icon" data-v-e033cd21><path d="M18,23H4c-1.7,0-3-1.3-3-3V6c0-1.7,1.3-3,3-3h7c0.6,0,1,0.4,1,1s-0.4,1-1,1H4C3.4,5,3,5.4,3,6v14c0,0.6,0.4,1,1,1h14c0.6,0,1-0.4,1-1v-7c0-0.6,0.4-1,1-1s1,0.4,1,1v7C21,21.7,19.7,23,18,23z"></path><path d="M8,17c-0.3,0-0.5-0.1-0.7-0.3C7,16.5,6.9,16.1,7,15.8l1-4c0-0.2,0.1-0.3,0.3-0.5l9.5-9.5c1.2-1.2,3.2-1.2,4.4,0c1.2,1.2,1.2,3.2,0,4.4l-9.5,9.5c-0.1,0.1-0.3,0.2-0.5,0.3l-4,1C8.2,17,8.1,17,8,17zM9.9,12.5l-0.5,2.1l2.1-0.5l9.3-9.3c0.4-0.4,0.4-1.1,0-1.6c-0.4-0.4-1.2-0.4-1.6,0l0,0L9.9,12.5z M18.5,2.5L18.5,2.5L18.5,2.5z"></path></svg> Edit this page on GitHub<!--]--><!----></a></div><div class="last-updated" data-v-e033cd21><p class="VPLastUpdated" data-v-e033cd21 data-v-355aa5ef>Last updated: <time datetime="2023-03-22T07:35:04.000Z" data-v-355aa5ef></time></p></div></div><!----></footer><!--[--><!--]--></div></div></div></div></div><footer class="VPFooter has-sidebar" data-v-93a960b4 data-v-d24360a6><div class="container" data-v-d24360a6><p class="message" data-v-d24360a6>Wrote with <i class="heart fa fa-heart fa-xs fa-beat"></i> and ☕ by <a href="https://toshiki.dev">Anda Toshiki</a> at <code>root@andatoshiki:/~</code></p><p class="copyright" data-v-d24360a6>Copyright © 2023-2023 <a href="https://github.com/andatoshiki">Anda Toshiki</a>
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