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Adding _.count to count truthy values in an iterator. _.count([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; }) = 3

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Samuel Clay
2011-04-05 18:09:47 -04:00
parent a9ac8b11f8
commit c8e3c04076
3 changed files with 34 additions and 6 deletions
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23
index.html
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@@ -137,12 +137,13 @@
<span class="methods"><a href="#each">each</a>, <a href="#map">map</a>, <span class="methods"><a href="#each">each</a>, <a href="#map">map</a>,
<a href="#reduce">reduce</a>, <a href="#reduceRight">reduceRight</a>, <a href="#reduce">reduce</a>, <a href="#reduceRight">reduceRight</a>,
<a href="#detect">detect</a>, <a href="#select">select</a>, <a href="#detect">detect</a>, <a href="#select">select</a>,
<a href="#reject">reject</a>, <a href="#all">all</a>, <a href="#reject">reject</a>, <a href="#count">count</a>,
<a href="#any">any</a>, <a href="#include">include</a>, <a href="#all">all</a>, <a href="#any">any</a>,
<a href="#invoke">invoke</a>, <a href="#pluck">pluck</a>, <a href="#include">include</a>, <a href="#invoke">invoke</a>,
<a href="#max">max</a>, <a href="#min">min</a>, <a href="#pluck">pluck</a>, <a href="#max">max</a>,
<a href="#sortBy">sortBy</a>, <a href="#sortedIndex">sortedIndex</a>, <a href="#min">min</a>, <a href="#sortBy">sortBy</a>,
<a href="#toArray">toArray</a>, <a href="#size">size</a></span> <a href="#sortedIndex">sortedIndex</a>, <a href="#toArray">toArray</a>,
<a href="#size">size</a></span>
</p> </p>
<p> <p>
@@ -337,6 +338,16 @@ var evens = _.select([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
<pre> <pre>
var odds = _.reject([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; }); var odds = _.reject([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=&gt; [1, 3, 5] =&gt; [1, 3, 5]
</pre>
<p id="count">
<b class="header">count</b><code>_.count(list, [iterator], [context])</code>
<br />
Returns a count of elements which pass the truth test (<b>iterator</b>).
</p>
<pre>
var count = _.count([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=&gt; 3
</pre> </pre>
<p id="all"> <p id="all">

7
test/collections.js
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@@ -122,6 +122,13 @@ $(document).ready(function() {
equals(odds.join(', '), '1, 3, 5', 'rejected each even number'); equals(odds.join(', '), '1, 3, 5', 'rejected each even number');
}); });
test('collections: count', function() {
var count = _.count([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
equals(count, 3, 'counted even numbers');
var count = _.count([0, 1, 2, 3, 4, 5, 6]);
equals(count, 6, 'counted all truthy numbers');
});
test('collections: all', function() { test('collections: all', function() {
ok(_.all([]), 'the empty set'); ok(_.all([]), 'the empty set');
ok(_.all([true, true, true]), 'all true values'); ok(_.all([true, true, true]), 'all true values');

10
underscore.js
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@@ -164,6 +164,16 @@
return results; return results;
}; };
// Returns a count of elements which pass a truth test.
_.count = function(obj, iterator, context) {
var count = 0;
iterator = iterator || _.identity;
each(obj, function(value, index, list) {
if (iterator.call(context, value, index, list)) count += 1;
});
return count;
};
// Determine whether all of the elements match a truth test. // Determine whether all of the elements match a truth test.
// Delegates to **ECMAScript 5**'s native `every` if available. // Delegates to **ECMAScript 5**'s native `every` if available.
// Aliased as `all`. // Aliased as `all`.