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<!DOCTYPE html> <html> <head> <title>_.array.selectors.js.md</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <meta name="viewport" content="width=device-width, target-densitydpi=160dpi, initial-scale=1.0; maximum-scale=1.0; user-scalable=0;"> <link rel="stylesheet" media="all" href="docco.css" /> </head> <body> <div id="container"> <div id="background"></div> <ul id="jump_to"> <li> <a class="large" href="javascript:void(0);">Jump To …</a> <a class="small" href="javascript:void(0);">+</a> <div id="jump_wrapper"> <div id="jump_page_wrapper"> <div id="jump_page"> <a class="source" href="_.array.builders.js.html"> _.array.builders.js.md </a> <a class="source" href="_.array.selectors.js.html"> _.array.selectors.js.md </a> <a class="source" href="_.collections.walk.js.html"> _.collections.walk.js.md </a> <a class="source" href="_.function.arity.js.html"> _.function.arity.js.md </a> <a class="source" href="_.function.combinators.js.html"> _.function.combinators.js.md </a> <a class="source" href="_.function.iterators.js.html"> _.function.iterators.js.md </a> <a class="source" href="_.function.predicates.js.html"> _.function.predicates.js.md </a> <a class="source" href="_.object.builders.js.html"> _.object.builders.js.md </a> <a class="source" href="_.object.selectors.js.html"> _.object.selectors.js.md </a> <a class="source" href="_.util.existential.js.html"> _.util.existential.js.md </a> <a class="source" href="_.util.operators.js.html"> _.util.operators.js.md </a> <a class="source" href="_.util.strings.js.html"> _.util.strings.js.md </a> <a class="source" href="_.util.trampolines.js.html"> _.util.trampolines.js.md </a> <a class="source" href="index.html"> index.md </a> </div> </div> </li> </ul> <ul class="sections"> <li id="title"> <div class="annotation"> <h1>_.array.selectors.js.md</h1> </div> </li> <li id="section-1"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-1">¶</a> </div> <h3 id="array-selectors">array.selectors</h3> <blockquote> <p>Functions to take things from arrays. <a href="docs/lodash.array.selectors.js.html" class="btn btn-primary btn-xs">View Annotated Source</a></p> </blockquote> <hr> </div> </li> <li id="section-2"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-2">¶</a> </div> <h4 id="best">best</h4> <p><strong>Signature:</strong> <code>_.best(array:Array, fun:Function)</code></p> <p>Returns the “best” value in an array based on the result of a given function.</p> <pre><code class="lang-javascript">_.best([<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>], <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">x, y</span>) </span>{ <span class="hljs-keyword">return</span> x > y; }); <span class="hljs-comment">//=> 5</span> </code></pre> <hr> </div> </li> <li id="section-3"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-3">¶</a> </div> <h4 id="dropwhile">dropWhile</h4> <p><strong>Signature:</strong> <code>_.dropWhile(array:Array, pred:Function)</code></p> <p>Drops elements for which the given function returns a truthy value.</p> <pre><code class="lang-javascript">_.dropWhile([-<span class="hljs-number">2</span>,-<span class="hljs-number">1</span>,<span class="hljs-number">0</span>,<span class="hljs-number">1</span>,<span class="hljs-number">2</span>], isNeg); <span class="hljs-comment">//=> [0,1,2]</span> </code></pre> <hr> </div> </li> <li id="section-4"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-4">¶</a> </div> <h4 id="keep">keep</h4> <p><strong>Signature:</strong> <code>_.keep(array:Array, fun:Function)</code></p> <p>Returns an array of existy results of a function over a source array.</p> <pre><code class="lang-javascript">_.keep([<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>], <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">val</span>) </span>{ <span class="hljs-keyword">if</span> (val % <span class="hljs-number">3</span> === <span class="hljs-number">0</span>) { <span class="hljs-keyword">return</span> val; } }); <span class="hljs-comment">// => [3]</span> </code></pre> <hr> </div> </li> <li id="section-5"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-5">¶</a> </div> <h4 id="nth">nth</h4> <p><strong>Signature:</strong> <code>_.nth(array:Array, index:Number[, guard:Any])</code></p> <p>The <code>_.nth</code> function is a convenience for the equivalent <code>array[n]</code>. The optional <code>guard</code> value allows <code>_.nth</code> to work correctly as a callback for <code>_.map</code>.</p> <pre><code class="lang-javascript">_.nth([<span class="hljs-string">'a'</span>,<span class="hljs-string">'b'</span>,<span class="hljs-string">'c'</span>], <span class="hljs-number">2</span>); <span class="hljs-comment">//=> 'c'</span> </code></pre> <p>If given an index out of bounds then <code>_.nth</code> will return <code>undefined</code>:</p> <pre><code class="lang-javascript">_.nth([<span class="hljs-string">'a'</span>,<span class="hljs-string">'b'</span>,<span class="hljs-string">'c'</span>], <span class="hljs-number">2000</span>); <span class="hljs-comment">//=> undefined</span> </code></pre> <p>The <code>_.nth</code> function can also be used in conjunction with <code>_.map</code> and <code>_.compact</code> like so:</p> <pre><code class="lang-javascript"><span class="hljs-keyword">var</span> b = [[<span class="hljs-string">'a'</span>],[<span class="hljs-string">'b'</span>],[]]; _.compact(_.map(b, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">e</span>) </span>{ <span class="hljs-keyword">return</span> _.nth(e,<span class="hljs-number">0</span>) })); <span class="hljs-comment">//=> ['a','b']</span> </code></pre> <p>If wrapping a function around <code>_.nth</code> is too tedious or you’d like to partially apply the index then Underscore-contrib offers any of <code>_.flip2</code>, <code>_.fix</code> or <code>_.curryRight2</code> to solve this.</p> <hr> </div> </li> <li id="section-6"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-6">¶</a> </div> <h4 id="partitionby">partitionBy</h4> <p><strong>Signature:</strong> <code>_.keep(array:Array, fun:Function)</code></p> <p>Takes an array and partitions it into sub-arrays as the given predicate changes truth sense.</p> <pre><code class="lang-javascript">_.partitionBy([<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">1</span>,<span class="hljs-number">1</span>,<span class="hljs-number">5</span>], _.isEven); <span class="hljs-comment">// => [[1],[2,2],[3,1,1,5]]</span> _.partitionBy([<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>,<span class="hljs-number">1</span>,<span class="hljs-number">1</span>,<span class="hljs-number">5</span>], _.identity); <span class="hljs-comment">// => [[1],[2,2],[3],[1,1],[5]]</span> </code></pre> <hr> </div> </li> <li id="section-7"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-7">¶</a> </div> <h4 id="second">second</h4> <p><strong>Signature:</strong> <code>_.second(array:Array, index:Number[, guard:Any])</code></p> <p>The <code>_.second</code> function is a convenience for the equivalent <code>array[1]</code>. The optional <code>guard</code> value allows <code>_.second</code> to work correctly as a callback for <code>_.map</code>.</p> <pre><code class="lang-javascript">_.second([<span class="hljs-string">'a'</span>,<span class="hljs-string">'b'</span>]); <span class="hljs-comment">//=> 'b'</span> _.map([[<span class="hljs-string">'a'</span>,<span class="hljs-string">'b'</span>], _.range(<span class="hljs-number">10</span>,<span class="hljs-number">20</span>)], _.second); <span class="hljs-comment">//=> ['b',11]</span> </code></pre> <p>You can also pass an optional number to the <code>_.second</code> function to take a number of elements from an array starting with the second element and ending at the given index:</p> <pre><code class="lang-javascript">_.second(_.range(<span class="hljs-number">10</span>), <span class="hljs-number">5</span>) <span class="hljs-comment">//=> [1, 2, 3, 4]</span> </code></pre> <hr> </div> </li> <li id="section-8"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-8">¶</a> </div> <h4 id="takewhile">takeWhile</h4> <p><strong>Signature:</strong> <code>_.takeWhile(array:Array, pred:Function)</code></p> <p>The <code>_.takeWhile</code> function takes an array and a function and returns a new array containing the first n elements in the original array for which the given function returns a truthy value:</p> <pre><code class="lang-javascript"><span class="hljs-keyword">var</span> isNeg = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">n</span>) </span>{ <span class="hljs-keyword">return</span> n < <span class="hljs-number">0</span>; }; _.takeWhile([-<span class="hljs-number">2</span>,-<span class="hljs-number">1</span>,<span class="hljs-number">0</span>,<span class="hljs-number">1</span>,<span class="hljs-number">2</span>], isNeg); <span class="hljs-comment">//=> [-2,-1]</span> </code></pre> <hr> </div> </li> <li id="section-9"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-9">¶</a> </div> <h4 id="third">third</h4> <p><strong>Signature:</strong> <code>_.third(array:Array, index:Number[, guard:Any])</code></p> <p>The <code>_.third</code> function is a convenience for the equivalent <code>array[2]</code>. The optional <code>guard</code> value allows <code>_.third</code> to work correctly as a callback for <code>_.map</code>.</p> <pre><code class="lang-javascript">_.third([<span class="hljs-string">'a'</span>,<span class="hljs-string">'b'</span>,<span class="hljs-string">'c'</span>]); <span class="hljs-comment">//=> 'c'</span> _.map([[<span class="hljs-string">'a'</span>,<span class="hljs-string">'b'</span>,<span class="hljs-string">'c'</span>], _.range(<span class="hljs-number">10</span>,<span class="hljs-number">20</span>)], _.third); <span class="hljs-comment">//=> ['c',12]</span> </code></pre> <p>You can also pass an optional number to the <code>_.third</code> function to take a number of elements from an array starting with the third element and ending at the given index:</p> <pre><code class="lang-javascript">_.third(_.range(<span class="hljs-number">10</span>), <span class="hljs-number">5</span>) <span class="hljs-comment">//=> [2, 3, 4]</span> </code></pre> <hr> </div> </li> <li id="section-10"> <div class="annotation"> <div class="pilwrap "> <a class="pilcrow" href="#section-10">¶</a> </div> </div> </li> </ul> </div> </body> </html>