ds-algo-study/DS-n-Algos/Arrays/flatten/flatten2.html

Just experimenting with publishing a package

<p>Flattens an array up to the specified depth.</p>
<ul>
  <li>Use recursion, decrementing <code>depth</code> by 1 for each level of depth.</li>
  <li>Use <code>Array..reduce()</code> and <code>Array..concat()</code> to merge elements or arrays.</li>
  <li>Base case, for <code>depth</code> equal to <code>1</code> stops recursion.</li>
  <li>Omit the second argument, <code>depth</code> to flatten only to a depth of <code>1</code> (single flatten).</li>
</ul>
<div id=">pre data-role=" codeBlock" data-info="js" class="language-javascript">
  <code><a   title="1"><span >function</span> <span >flatten</span>(arr<span >,</span> depth <span >=</span> <span >1</span>) <span >{</span></a>
<a   title="2">  <span >return</span> <span >arr</span>.<span >reduce</span>((newArr<span >,</span> curEle) <span >=&gt;</span> <span >{</span></a>
<a   title="3">    <span >if</span> (depth <span >&gt;</span> <span >1</span> <span >&amp;&amp;</span> <span >Array</span>.<span >isArray</span>(curEle)) <span >{</span></a>
<a   title="4">      <span >return</span> <span >newArr</span>.<span >concat</span>(<span >flatten</span>(curEle<span >,</span> depth <span >-</span> <span >1</span>))<span >;</span></a>
<a   title="5">    <span >}</span> <span >else</span> <span >{</span></a>
<a  id=-6" title="6">      <span >return</span> <span >newArr</span>.<span >concat</span>(curEle)<span >;</span></a>
<a   title="7">    <span >}</span></a>
<a   title="8">  <span >},</span> [])<span >;</span></a>
<a   title="9"><span >}</span></a>
<a id=-10" title="10"><span>console</span>.<span>log</span>(<span>&quot;flatten([1, [2], 3, 4], 3): &quot;,</span>
  <span>flatten</span>([<span>1,</span> [<span>2</span>]<span>,</span> <span>3,</span> <span>4</span>]<span>,</span>
  <span>3</span>))<span>;</span></a></code>
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<div id=">pre data-role=" codeBlock" data-info="js" class="language-javascript">
  <code><a   title="1"><span >flatten</span>([<span >1,</span> <span >&quot;a&quot;,</span> [<span >&quot;hello&quot;,</span> [<span >&quot;world&quot;,</span> <span >&quot;1&quot;</span>]]])</a>
<a  id=-2" title="2"><span >flatten</span>([<span >1,</span> [<span >2</span>]<span >,</span> <span >3,</span> <span >4</span>])<span >;</span> <span >// [1, 2, 3, 4]</span></a>
<a id=-3" title="3"><span>flatten</span>([<span>1,</span> [<span>2,</span> [<span>3,</span> [<span>4,</span>
  <span>5</span>]<span>,</span> <span>6</span>]<span>,</span> <span>7</span>]<span>,</span>
  <span>8</span>]<span>,</span> <span>2</span>)<span>;</span> <span>// [1, 2, 3, [4, 5], 6, 7, 8]</span></a></code>
</pre>
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