blocks|key|1138623|text|您应该能够使用reduce。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1138624|var+sum+=+array.reduce(function(pv,+cv)+{+return+pv+%2B+cv;+},+0);|code-block|syntax|javascript|1138625|Source|1138626|而在ES6中引入了arrow+functions，事情就更简单了：|1138627|sum+=+array.reduce((pv,+cv)+=>+pv+%2B+cv,+0);|1138628|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/Reduce|1|https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions^0|7|6|0|0|0|6|0|0|9|F|1|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|D|@$9|15|A|16|1|17]]|E|$]]|$1|M|3|N|5|6|7|18|8|@]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|O|3|P|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

You should be able to use <code>reduce</code>.

<pre><code>var sum = array.reduce(function(pv, cv) { return pv + cv; }, 0);
</code></pre>

<a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/Reduce" rel="noreferrer">Source</a>

And with <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions" rel="noreferrer">arrow functions</a> introduced in ES6, it's even simpler:

<pre><code>sum = array.reduce((pv, cv) =&gt; pv + cv, 0);
</code></pre>

blocks|key|1138952|text|在寻找数组求和的最佳方法时，我写了一个性能测试。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1138953|在Chrome中，"reduce“似乎要优越得多|1138954|我希望这能帮到你|1138955|//+Performance+test,+sum+of+an+array
++var+array+=+[1,+2,+3,+4,+5,+6,+7,+8,+9,+10];
++var+result+=+0;
//+Eval
++console.time("eval");
++for(var+i+=+0;+i+<+10000;+i%2B%2B)+eval("result+=+("+%2B+array.join("%2B")+%2B+")");
++console.timeEnd("eval");
//+Loop
++console.time("loop");
++for(var+i+=+0;+i+<+10000;+i%2B%2B){
++++result+=+0;
++++for(var+j+=+0;+j+<+array.length;+j%2B%2B){
++++++result+%2B=+parseInt(array[j]);
++++}
++}
++console.timeEnd("loop");
//+Reduce
++console.time("reduce");
++for(var+i+=+0;+i+<+10000;+i%2B%2B)+result+=+array.reduce(function(pv,+cv)+{+return+pv+%2B+parseInt(cv);+},+0);
++console.timeEnd("reduce");
//+While
++console.time("while");
++for(var+i+=+0;+i+<+10000;+i%2B%2B){
++++j+=+array.length;
++++result+=+0;
++++while(j--)+result+%2B=+array[i];
++}
++console.timeEnd("while");|code-block|syntax|javascript|1138956|eval:+5233.000ms|1138957|循环时间:+255.000ms|1138958|reduce:+70.000ms|1138959|而:+214.000ms|1138960|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

While searching for the best method to sum an array, I wrote a performance test.

In Chrome, "reduce" seems to be vastly superior

I hope this helps

<pre><code>// Performance test, sum of an array
 var array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
 var result = 0;
// Eval
 console.time("eval");
 for(var i = 0; i &lt; 10000; i++) eval("result = (" + array.join("+") + ")");
 console.timeEnd("eval");
// Loop
 console.time("loop");
 for(var i = 0; i &lt; 10000; i++){
 result = 0;
 for(var j = 0; j &lt; array.length; j++){
 result += parseInt(array[j]);
 }
 }
 console.timeEnd("loop");
// Reduce
 console.time("reduce");
 for(var i = 0; i &lt; 10000; i++) result = array.reduce(function(pv, cv) { return pv + parseInt(cv); }, 0);
 console.timeEnd("reduce");
// While
 console.time("while");
 for(var i = 0; i &lt; 10000; i++){
 j = array.length;
 result = 0;
 while(j--) result += array[i];
 }
 console.timeEnd("while");
</code></pre>

eval: 5233.000ms

loop: 255.000ms

reduce: 70.000ms

while: 214.000ms

blocks|key|924516|text|或者你可以用邪恶的方式来做。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|924517|var+a+=+[1,2,3,4,5,6,7,8,9];

sum+=+eval(a.join("%2B"));|code-block|syntax|javascript|924518|;)|924519|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Or you could do it the evil way.

<pre><code>var a = [1,2,3,4,5,6,7,8,9];

sum = eval(a.join("+"));
</code></pre>

;)

blocks|key|924219|text|根据this+test的说法，最快的循环是反向的while循环|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|924220|var+i+=+arr.length;+while+(i--)+{+}|code-block|syntax|javascript|924221|所以，这段代码可能是你能得到的最快的|924222|Array.prototype.sum+=+function+()+{
++++var+total+=+0;
++++var+i+=+this.length;+

++++while+(i--)+{
++++++++total+%2B=+this[i];
++++}

++++return+total;
}|924223|Array.prototype.sum向数组类添加了一个sum方法...你可以很容易地把它变成一个帮助器函数。|style|CODE|924224|entityMap|0|LINK|mutability|MUTABLE|url|http://blogs.oracle.com/greimer/resource/loop-test.html^0|2|9|0|0|0|0|0|0|J|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|14|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|15|8|@$A|16|B|17|O|P]]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|18|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

The fastest loop, according to <a href="http://blogs.oracle.com/greimer/resource/loop-test.html" rel="noreferrer">this test</a> is a while loop in reverse

<pre><code>var i = arr.length; while (i--) { }
</code></pre>

So, this code might be the fastest you can get

<pre><code>Array.prototype.sum = function () {
 var total = 0;
 var i = this.length; 

 while (i--) {
 total += this[i];
 }

 return total;
}
</code></pre>

<code>Array.prototype.sum</code> adds a sum method to the array class... you could easily make it a helper function instead.

blocks|key|924266|text|对于您的特定情况，只需使用数组的reduce方法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|924267|var+sumArray+=+function()+{
++++//+Use+one+adding+function+rather+than+create+a+new+one+each
++++//+time+sumArray+is+called
++++function+add(a,+b)+{
++++++++return+a+%2B+b;
++++}

++++return+function(arr)+{
++++++++return+arr.reduce(add);
++++};
}();

alert(+sumArray([2,+3,+4])+);|code-block|syntax|javascript|924268|entityMap^0|G|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

For your specific case, just use the <code>reduce</code> method of Arrays:

<pre><code>var sumArray = function() {
 // Use one adding function rather than create a new one each
 // time sumArray is called
 function add(a, b) {
 return a + b;
 }

 return function(arr) {
 return arr.reduce(add);
 };
}();

alert( sumArray([2, 3, 4]) );
</code></pre>

blocks|key|1138887|text|基于this+test+(for-vs-forEach-vs-reduce)和this+(loops)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1138888|我可以这么说：|1138889|1#最快:+for循环|1138890|var+total+=+0;

for+(var+i+=+0,+n+=+array.length;+i+<+n;+%2B%2Bi)
{
++++total+%2B=+array[i];
}|code-block|syntax|javascript|1138891|2#聚合|1138892|对于您的情况，您不需要这个，但它增加了很多灵活性。|1138893|Array.prototype.Aggregate+=+function(fn)+{
++++var+current
++++++++,+length+=+this.length;

++++if+(length+==+0)+throw+"Reduce+of+empty+array+with+no+initial+value";

++++current+=+this[0];

++++for+(var+i+=+1;+i+<+length;+%2B%2Bi)
++++{
++++++++current+=+fn(current,+this[i]);
++++}

++++return+current;
};|1138894|用法：|1138895|var+total+=+array.Aggregate(function(a,b){+return+a+%2B+b+});|1138896|不确定的方法|1138897|然后是forEach和reduce，它们的性能几乎相同，并且在不同的浏览器中有所不同，但无论如何，它们的性能是最差的。|style|CODE|1138898|entityMap|0|LINK|mutability|MUTABLE|url|http://jsperf.com/array-reduce-vs-foreach/2|1|http://jsperf.com/loops/98^0|2|10|0|13|C|1|0|0|0|0|0|0|0|0|0|0|3|7|B|6|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@$A|1D|B|1E|1|1F]|$A|1G|B|1H|1|1I]]|C|$]]|$1|D|3|E|5|6|7|1J|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|1K|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|1L|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|1M|8|@]|9|@]|C|$]]|$1|O|3|P|5|6|7|1N|8|@]|9|@]|C|$]]|$1|Q|3|R|5|J|7|1O|8|@]|9|@]|C|$K|L]]|$1|S|3|T|5|6|7|1P|8|@]|9|@]|C|$]]|$1|U|3|V|5|J|7|1Q|8|@]|9|@]|C|$K|L]]|$1|W|3|X|5|6|7|1R|8|@]|9|@]|C|$]]|$1|Y|3|Z|5|6|7|1S|8|@$A|1T|B|1U|10|11]|$A|1V|B|1W|10|11]]|9|@]|C|$]]|$1|12|3|-4|5|6|7|1X|8|@]|9|@]|C|$]]]|13|$14|$5|15|16|17|C|$18|19]]|1A|$5|15|16|17|C|$18|1B]]]]

Based on <a href="http://jsperf.com/array-reduce-vs-foreach/2" rel="nofollow">this test (for-vs-forEach-vs-reduce)</a> and <a href="http://jsperf.com/loops/98" rel="nofollow">this (loops)</a>

I can say that:

<h2>1# Fastest: for loop</h2>

<pre><code>var total = 0;

for (var i = 0, n = array.length; i &lt; n; ++i)
{
 total += array[i];
}
</code></pre>

<h2>2# Aggregate</h2>

For you case you won't need this, but it adds a lot of flexibility.

<pre><code>Array.prototype.Aggregate = function(fn) {
 var current
 , length = this.length;

 if (length == 0) throw "Reduce of empty array with no initial value";

 current = this[0];

 for (var i = 1; i &lt; length; ++i)
 {
 current = fn(current, this[i]);
 }

 return current;
};
</code></pre>

Usage:

<pre><code>var total = array.Aggregate(function(a,b){ return a + b });
</code></pre>

<h2>Inconclusive methods</h2>

Then comes <code>forEach</code> and <code>reduce</code> which have almost the same performance and varies from browser to browser, but they have the worst performance anyway.

blocks|key|924492|text|最简单、最快、更可重用和更灵活的方法之一是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|924493|Array.prototype.sum+=+function+()+{
++++for(var+total+=+0,l=this.length;l--;total%2B=this[l]);+return+total;
}

//+usage
var+array+=+[1,2,3,4,5,6,7,8,9,10];
array.sum()|code-block|syntax|javascript|924494|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

one of the simplest, fastest, more reusable and flexible is:

<pre><code>Array.prototype.sum = function () {
 for(var total = 0,l=this.length;l--;total+=this[l]); return total;
}

// usage
var array = [1,2,3,4,5,6,7,8,9,10];
array.sum()
</code></pre>

blocks|key|1139072|text|两端求和如何？它会把时间缩短一半。如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1139073|1、2、3、4、5、6、7、8；sum+=0|1139074|2，3，4，5，6，7；sum+=+10|1139075|3，4，5，6；sum+=+19|1139076|4，5；sum+=+28|1139077|sum+=+37|1139078|一种算法可以是：|1139079|function+sum_array(arr){
++++let+sum+=+0,
++++++++length+=+arr.length,
++++++++half+=+Math.floor(length/2)

++++for+(i+=+0;+i+<+half;+i%2B%2B)+{
++++++++sum+%2B=+arr[i]+%2B+arr[length+-+1+-+i]
++++}
++++if+(length%252){
++++++++sum+%2B=+arr[half]
++++}
++++return+sum
}|code-block|syntax|javascript|1139080|当我用performance.now()在浏览器上测试它时，它的执行速度更快。我认为这是一种更好的方式。你们觉得怎么样？|offset|length|style|CODE|1139081|entityMap^0|0|0|0|0|0|0|0|0|3|H|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|13|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|14|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|15|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|16|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|17|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|18|8|@$U|19|V|1A|W|X]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

What about summing both extremities? It would cut time in half. Like so:

1, 2, 3, 4, 5, 6, 7, 8; sum = 0

2, 3, 4, 5, 6, 7; sum = 10

3, 4, 5, 6; sum = 19

4, 5; sum = 28

sum = 37

One algorithm could be:

<pre><code>function sum_array(arr){
 let sum = 0,
 length = arr.length,
 half = Math.floor(length/2)

 for (i = 0; i &lt; half; i++) {
 sum += arr[i] + arr[length - 1 - i]
 }
 if (length%2){
 sum += arr[half]
 }
 return sum
}
</code></pre>

It performs faster when I test it on the browser with <code>performance.now()</code>.
I think this is a better way. What do you guys think?

What is the fastest way to sum up an array in JavaScript? A quick search turns over <a href="http://www.gscottolson.com/weblog/2007/12/09/sum-array-prototype-for-javascript/" rel="noreferrer">a few different methods</a>, but I would like a native solution if possible. This will run under SpiderMonkey. 

Thinking very inside-the-box I have been using:

<pre><code>var count = 0;
for(var i = 0; i &lt; array.length; i++)
{
 count = count + array[i];
}
</code></pre>

I'm sure there is a better way then straight iteration.

Fastest JavaScript summation

性能测试

在JavaScript中对数组求和的最快方法是什么？快速搜索一下，但如果可能的话，我想要一个本机解决方案。这将在SpiderMonkey下运行。在我一直使用的盒子里思考：var count = 0;for(var i = 0; i < array.length; i++){ count = count + array[i];}我相信有一种比直接迭代更好的方法。

问最快的JavaScript求和
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