Fastest JavaScript summation

Question

What is the fastest way to sum up an array in JavaScript? A quick search turns over a few different methods, but I would like a native solution if possible. This will run un

Answer 1

Based on this test (for-vs-forEach-vs-reduce) and this (loops)

I can say that:

1# Fastest: for loop

var total = 0;

for (var i = 0, n = array.length; i < n; ++i)
{
    total += array[i];
}

2# Aggregate

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

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; ++i)
    {
        current = fn(current, this[i]);
    }

    return current;
};

Usage:

var total = array.Aggregate(function(a,b){ return a + b });

Inconclusive methods

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

Answer 2

You should be able to use reduce.

var sum = array.reduce(function(pv, cv) { return pv + cv; }, 0);

Source

And with arrow functions introduced in ES6, it's even simpler:

sum = array.reduce((pv, cv) => pv + cv, 0);

Answer 3

The fastest loop, according to this test is a while loop in reverse

var i = arr.length; while (i--) { }

So, this code might be the fastest you can get

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

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

    return total;
}

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

Answer 4

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

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()