I was wondering if anyone knows of a nice way of adding an array of values in javascript?

I came up with:

var myArray = [1,2,3,4,5];

var total = eval(myArray.join("+"));

Which is nice and short, but I'm guessing going from num to string and then evaling to get back to a number is a slow way of getting the total.

I was wondering if anyone knows of a nice way of adding an array of values in javascript?

I came up with:

var myArray = [1,2,3,4,5];

var total = eval(myArray.join("+"));

Which is nice and short, but I'm guessing going from num to string and then evaling to get back to a number is a slow way of getting the total.

• javascript
• arrays
• optimization

• Yep I'd say that's definitely inefficient! – El Ronnoco Commented Feb 10, 2011 at 12:26
• 1 Why would you avoid loops? Much less use eval for this? – user395760 Commented Feb 10, 2011 at 12:27
• 1 eval is evil. Didn't you get the memo? – Andy E Commented Feb 10, 2011 at 12:35
• Possible duplicate of How to find the sum of an array of numbers – Mohammad Usman Commented Sep 30, 2018 at 11:20

2 Answers 2

The most appropriate method of doing this is to use the [Array.prototype.reduce]( https://developer.mozilla/en/JavaScript/Reference/Global_Objects/Array/reduce) function, an addition to the language in ECMAScript 5th Edition:

var myArray = [1,2,3,4,5],
    total   =  myArray.reduce(function (curr, prev) { return curr + prev; });

alert(total);

Of course, this isn't supported in older browsers so you might want to include the patibility implementation in your code.

UPDATE - To bine Andy's method and the Prototyping method...

Array.prototype.sum = function(){
    return this.reduce(function(a,b) {return a+b} );
}

Now all array will have the sum method. eg var total = myArray.sum();.

Original answer...

I'd be tempted with just

var myArray = [1,2,3,4,5];
var sum     = 0;

for (var i=0, iMax=myArray.length; i < iMax; i++){
    sum += myArray[i];
};

alert(sum);

break it out into a function if you're using it a lot. Or even neater, prototype it...

Array.prototype.sum = function(){
    for(var i=0, sum=0, max=this.length; i < max; sum += this[i++]);
    return sum;  
}

var myArray = [1,2,3,4,5];

alert(myArray.sum());

Courtesy of DZone Snippets