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Ensuring code quality</a></li><li><a href="/javascript/anti-patterns.html" class="sidebar-link">Anti-patterns</a></li><li><a href="/javascript/performance-tips.html" class="sidebar-link">Performance Tips</a></li><li><a href="/javascript/memory-efficiency.html" class="sidebar-link">Memory efficiency</a></li><li><a href="/javascript/reserved-keywords.html" class="sidebar-link">Reserved Keywords</a></li><li><a href="/javascript/contributors.html" class="sidebar-link">The Contributors</a></li></ul></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="data-manipulation"><a href="#data-manipulation" class="header-anchor">#</a> Data Manipulation</h1> <h2 id="format-numbers-as-money"><a href="#format-numbers-as-money" class="header-anchor">#</a> Format numbers as money</h2> <p>Fast and short way to format value of type <code>Number</code> as money, e.g. <code>1234567.89 => "1,234,567.89"</code>:</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">var</span> num <span class="token operator">=</span> <span class="token number">1234567.89</span><span class="token punctuation">,</span>
formatted<span class="token punctuation">;</span>
formatted <span class="token operator">=</span> num<span class="token punctuation">.</span><span class="token function">toFixed</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">replace</span><span class="token punctuation">(</span><span class="token regex"><span class="token regex-delimiter">/</span><span class="token regex-source language-regex">\d(?=(\d{3})+\.)</span><span class="token regex-delimiter">/</span><span class="token regex-flags">g</span></span><span class="token punctuation">,</span> <span class="token string">'$&,'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// "1,234,567.89"</span>
</code></pre></div><p>More advanced variant with support of any number of decimals <code>[0 .. n]</code>, variable size of number groups <code>[0 .. x]</code> and different delimiter types:</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token comment">/**
* Number.prototype.format(n, x, s, c)
*
* @param integer n: length of decimal
* @param integer x: length of whole part
* @param mixed s: sections delimiter
* @param mixed c: decimal delimiter
*/</span>
<span class="token class-name">Number</span><span class="token punctuation">.</span>prototype<span class="token punctuation">.</span><span class="token function-variable function">format</span> <span class="token operator">=</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">n<span class="token punctuation">,</span> x<span class="token punctuation">,</span> s<span class="token punctuation">,</span> c</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">var</span> re <span class="token operator">=</span> <span class="token string">'\\d(?=(\\d{'</span> <span class="token operator">+</span> <span class="token punctuation">(</span>x <span class="token operator">||</span> <span class="token number">3</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">'})+'</span> <span class="token operator">+</span> <span class="token punctuation">(</span>n <span class="token operator">></span> <span class="token number">0</span> <span class="token operator">?</span> <span class="token string">'\\D'</span> <span class="token operator">:</span> <span class="token string">'$'</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">')'</span><span class="token punctuation">,</span>
num <span class="token operator">=</span> <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">toFixed</span><span class="token punctuation">(</span>Math<span class="token punctuation">.</span><span class="token function">max</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token operator">~</span><span class="token operator">~</span>n<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">return</span> <span class="token punctuation">(</span>c <span class="token operator">?</span> num<span class="token punctuation">.</span><span class="token function">replace</span><span class="token punctuation">(</span><span class="token string">'.'</span><span class="token punctuation">,</span> c<span class="token punctuation">)</span> <span class="token operator">:</span> num<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">replace</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">RegExp</span><span class="token punctuation">(</span>re<span class="token punctuation">,</span> <span class="token string">'g'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">'$&'</span> <span class="token operator">+</span> <span class="token punctuation">(</span>s <span class="token operator">||</span> <span class="token string">','</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token number">12345678.9</span><span class="token punctuation">.</span><span class="token function">format</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'.'</span><span class="token punctuation">,</span> <span class="token string">','</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// "12.345.678,90"</span>
<span class="token number">123456.789</span><span class="token punctuation">.</span><span class="token function">format</span><span class="token punctuation">(</span><span class="token number">4</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token string">' '</span><span class="token punctuation">,</span> <span class="token string">':'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// "12 3456:7890"</span>
<span class="token number">12345678.9</span><span class="token punctuation">.</span><span class="token function">format</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'-'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// "12-345-679"</span>
<span class="token number">123456789.</span><span class="token punctuation">.</span><span class="token function">format</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// "123,456,789.00"</span>
</code></pre></div><h2 id="extract-extension-from-file-name"><a href="#extract-extension-from-file-name" class="header-anchor">#</a> Extract extension from file name</h2> <p>Fast and short way to extract extension from file name in JavaScript will be:</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token parameter">filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">return</span> filename<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">(</span><span class="token punctuation">(</span>filename<span class="token punctuation">.</span><span class="token function">lastIndexOf</span><span class="token punctuation">(</span><span class="token string">'.'</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">1</span> <span class="token operator">>>></span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
</code></pre></div><p>It works correctly both with names having no extension (e.g. <code>myfile</code>) or starting with <code>.</code> dot (e.g. <code>.htaccess</code>):</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token string">''</span><span class="token punctuation">)</span> <span class="token comment">// ""</span>
<span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token string">'name'</span><span class="token punctuation">)</span> <span class="token comment">// ""</span>
<span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token string">'name.txt'</span><span class="token punctuation">)</span> <span class="token comment">// "txt"</span>
<span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token string">'.htpasswd'</span><span class="token punctuation">)</span> <span class="token comment">// ""</span>
<span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token string">'name.with.many.dots.myext'</span><span class="token punctuation">)</span> <span class="token comment">// "myext"</span>
</code></pre></div><p>The following solution may extract file extensions from full path:</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token parameter">path</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">var</span> basename <span class="token operator">=</span> path<span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token regex"><span class="token regex-delimiter">/</span><span class="token regex-source language-regex">[\\/]</span><span class="token regex-delimiter">/</span></span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">pop</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token comment">// extract file name from full path ...</span>
<span class="token comment">// (supports `\\` and `/` separators)</span>
pos <span class="token operator">=</span> basename<span class="token punctuation">.</span><span class="token function">lastIndexOf</span><span class="token punctuation">(</span><span class="token string">'.'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// get last position of `.`</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>basename <span class="token operator">===</span> <span class="token string">''</span> <span class="token operator">||</span> pos <span class="token operator"><</span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token comment">// if file name is empty or ...</span>
<span class="token keyword">return</span> <span class="token string">""</span><span class="token punctuation">;</span> <span class="token comment">// `.` not found (-1) or comes first (0)</span>
<span class="token keyword">return</span> basename<span class="token punctuation">.</span><span class="token function">slice</span><span class="token punctuation">(</span>pos <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// extract extension ignoring `.`</span>
<span class="token punctuation">}</span>
<span class="token function">get_extension</span><span class="token punctuation">(</span><span class="token string">'/path/to/file.ext'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// "ext"</span>
</code></pre></div><h2 id="set-object-property-given-its-string-name"><a href="#set-object-property-given-its-string-name" class="header-anchor">#</a> Set object property given its string name</h2> <div class="language-js extra-class"><pre class="language-js"><code><span class="token keyword">function</span> <span class="token function">assign</span><span class="token punctuation">(</span><span class="token parameter">obj<span class="token punctuation">,</span> prop<span class="token punctuation">,</span> value</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token keyword">typeof</span> prop <span class="token operator">===</span> <span class="token string">'string'</span><span class="token punctuation">)</span>
prop <span class="token operator">=</span> prop<span class="token punctuation">.</span><span class="token function">split</span><span class="token punctuation">(</span><span class="token string">'.'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span>prop<span class="token punctuation">.</span>length <span class="token operator">></span> <span class="token number">1</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">var</span> e <span class="token operator">=</span> prop<span class="token punctuation">.</span><span class="token function">shift</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">assign</span><span class="token punctuation">(</span>obj<span class="token punctuation">[</span>e<span class="token punctuation">]</span> <span class="token operator">=</span>
<span class="token class-name">Object</span><span class="token punctuation">.</span>prototype<span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">.</span><span class="token function">call</span><span class="token punctuation">(</span>obj<span class="token punctuation">[</span>e<span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token operator">===</span> <span class="token string">'[object Object]'</span>
<span class="token operator">?</span> obj<span class="token punctuation">[</span>e<span class="token punctuation">]</span>
<span class="token operator">:</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
prop<span class="token punctuation">,</span>
value<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword">else</span>
obj<span class="token punctuation">[</span>prop<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token operator">=</span> value<span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token keyword">var</span> obj <span class="token operator">=</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">,</span>
propName <span class="token operator">=</span> <span class="token string">'foo.bar.foobar'</span><span class="token punctuation">;</span>
<span class="token function">assign</span><span class="token punctuation">(</span>obj<span class="token punctuation">,</span> propName<span class="token punctuation">,</span> <span class="token string">'Value'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// obj == {</span>
<span class="token comment">// foo : {</span>
<span class="token comment">// bar : {</span>
<span class="token comment">// foobar : 'Value'</span>
<span class="token comment">// }</span>
<span class="token comment">// }</span>
<span class="token comment">// }</span>
</code></pre></div></div> <footer class="page-edit"><div class="edit-link"><a href="https://github.com/devtut/generate/edit/master/docs/javascript/data-manipulation.md" target="_blank" rel="noopener noreferrer">Edit this page on GitHub</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----></footer> <div class="page-nav"><p class="inner"><span class="prev">
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