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@ -35,9 +35,10 @@
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}
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</script>
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<body>
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<a href="https://github.com/Chalarangelo/30-seconds-of-code" class="github-corner" aria-label="View source on Github"><svg width="90" height="90" viewBox="0 0 250 250" style="fill:#151513; color:#fff; position: absolute; top: 0; border: 0; right: 0;" aria-hidden="true"><path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path><path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2" fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path><path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z" fill="currentColor" class="octo-body"></path></svg></a><style>.github-corner:hover .octo-arm{animation:octocat-wave 560ms ease-in-out}@keyframes octocat-wave{0%,100%{transform:rotate(0)}20%,60%{transform:rotate(-25deg)}40%,80%{transform:rotate(10deg)}}@media (max-width:500px){.github-corner:hover .octo-arm{animation:none}.github-corner .octo-arm{animation:octocat-wave 560ms ease-in-out}}</style>
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<header style="height: 5.5rem;">
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<h1 class="logo" style="margin-top: -0.8rem; text-align:center;"><a style="text-decoration:none;color:black" href="https://github.com/Chalarangelo/30-seconds-of-code"><img src="favicon.png" style="height: 4rem;"/><span style="position:relative; top: -1rem;"> 30 seconds of code</span></a>
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<span style="display:block; font-size: 1rem; font-style: italic; color: grey; margin-top: -0.8rem">Curated collection of useful Javascript snippets that you can understand in 30 seconds or less.</span>
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<span style="display:block; font-size: 1rem; font-style: italic; color: grey; margin-top: -0.8rem">Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.</span>
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</h1>
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<label for="doc-drawer-checkbox" class="button drawer-toggle" style="position: absolute; right: 0; top: 0;"></label>
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</header>
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@ -330,7 +331,7 @@ Use <code>Array.reduce()</code> to create an object, where the keys are produced
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<p>Initializes an array containing the numbers in the specified range where <code>start</code> and <code>end</code> are inclusive.</p>
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<p>Use <code>Array((end + 1) - start)</code> to create an array of the desired length, <code>Array.map()</code> to fill with the desired values in a range.
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You can omit <code>start</code> to use a default value of <code>0</code>.</p>
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<pre><code class="language-js">const initializeArrayWithRange = (end, start = 0) =>
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<pre><code class="language-js">const initializeArrayWithRange = (end, start = 0) =>
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Array.from({ length: (end + 1) - start }).map((v, i) => i + start);
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// initializeArrayWithRange(5) -> [0,1,2,3,4,5]
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// initializeArrayWithRange(7, 3) -> [3,4,5,6,7]
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@ -357,7 +358,7 @@ You can omit <code>value</code> to use a default value of <code>0</code>.</p>
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</div></div><br/><div class="card fluid"><div class="section double-padded"><h3 id="mapobject">mapObject</h3></div><div class="section double-padded">
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<p>Maps the values of an array to an object using a function, where the key-value pairs consist of the original value as the key and the mapped value.</p>
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<p>Use an anonymous inner function scope to declare an undefined memory space, using closures to store a return value. Use a new <code>Array</code> to stor the array with a map of the function over its data set and a comma operator to return a second step, without needing to move from one context to another (due to closures and order of operations).</p>
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<pre><code class="language-js">const mapObject = (arr, fn) =>
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<pre><code class="language-js">const mapObject = (arr, fn) =>
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(a => (a = [arr, arr.map(fn)], a[0].reduce( (acc,val,ind) => (acc[val] = a[1][ind], acc), {}) )) ( );
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/*
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const squareIt = arr => mapObject(arr, a => a*a)
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@ -407,7 +408,7 @@ Use <code>Array.push()</code> to keep track of pulled values</p>
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let removed = [];
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let pulled = arr.map((v, i) => pullArr.includes(i) ? removed.push(v) : v)
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.filter((v, i) => !pullArr.includes(i))
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arr.length = 0;
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arr.length = 0;
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pulled.forEach(v => arr.push(v));
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return removed;
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}
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@ -424,7 +425,7 @@ Use <code>Array.push()</code> to keep track of pulled values</p>
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Use <code>Array.length = 0</code> to mutate the passed in array by resetting it's length to zero and <code>Array.push()</code> to re-populate it with only the pulled values.
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Use <code>Array.push()</code> to keep track of pulled values</p>
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<pre><code class="language-js">const pullAtValue = (arr, pullArr) => {
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let removed = [],
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let removed = [],
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pushToRemove = arr.forEach((v, i) => pullArr.includes(v) ? removed.push(v) : v),
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mutateTo = arr.filter((v, i) => !pullArr.includes(v));
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arr.length = 0;
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@ -786,7 +787,7 @@ Count and return the number of <code>1</code>s in the string, using <code>match(
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</div></div><br/><div class="card fluid"><div class="section double-padded"><h3 id="isarmstrongnumber">isArmstrongNumber</h3></div><div class="section double-padded">
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<p>Checks if the given number is an armstrong number or not.</p>
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<p>Convert the given number into array of digits. Use <code>Math.pow()</code> to get the appropriate power for each digit and sum them up. If the sum is equal to the number itself, return <code>true</code> otherwise <code>false</code>.</p>
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<pre><code class="language-js">const isArmstrongNumber = digits =>
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<pre><code class="language-js">const isArmstrongNumber = digits =>
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( arr => arr.reduce( ( a, d ) => a + Math.pow( parseInt( d ), arr.length ), 0 ) == digits ? true : false )( ( digits+'' ).split( '' ) );
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// isArmstrongNumber(1634) -> true
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// isArmstrongNumber(371) -> true
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@ -1251,7 +1252,7 @@ Use <code>Number()</code> to check if the coercion holds.</p>
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</code></pre>
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</div></div><br/>
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<footer>
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<p style="display: inline-block;"><strong>30 seconds of code</strong> is licensed under the <a href="https://github.com/Chalarangelo/30-seconds-of-code/blob/master/LICENSE">CC0-1.0</a> license.<br/>Icons made by <a href="https://www.flaticon.com/authors/smashicons">Smashicons</a> from <a href="https://www.flaticon.com/">www.flaticon.com</a> is licensed by <a href="http://creativecommons.org/licenses/by/3.0/">CC 3.0 BY</a>.</p>
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<p style="display: inline-block;"><strong>30 seconds of code</strong> is licensed under the <a href="https://github.com/Chalarangelo/30-seconds-of-code/blob/master/LICENSE">CC0-1.0</a> license.<br/>Icons made by <a href="https://www.flaticon.com/authors/smashicons">Smashicons</a> from <a href="https://www.flaticon.com/">www.flaticon.com</a> is licensed by <a href="http://creativecommons.org/licenses/by/3.0/">CC 3.0 BY</a>.</br>Ribbon made by <a href="https://github.com/tholman/github-corners">Tim Holman</a> is licensed by <a href="https://opensource.org/licenses/MIT">The MIT License</a></p>
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<a href="#top"><p style="display: inline-block;float: right;padding-right: 2em;">Back to top</p></a>
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</footer>
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</main>
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Angelos Chalaris
GitHub