Sum an Array of Numbers with JavaScript

By  on  

It's rare that I'm disappointed by the JavaScript language not having a function that I need. One such case was summing an array of numbers -- I was expecting Math.sum or a likewise, baked in API. Fear not -- summing an array of numbers is easy using Array.prototype.reduce!

const numbers = [1, 2, 3, 4];
const sum = numbers.reduce((a, b) => a + b, 0);

The 0 represents the starting value while with a and b, one represents the running total with the other representing the value to be added. You'll also note that using reduce prevents side effects! I'd still prefer something like Math.sum(...numbers) but a simple reduce will do!

Recent Features

  • By
    JavaScript Promise API

    While synchronous code is easier to follow and debug, async is generally better for performance and flexibility. Why "hold up the show" when you can trigger numerous requests at once and then handle them when each is ready?  Promises are becoming a big part of the JavaScript world...

  • By
    From Webcam to Animated GIF: the Secret Behind chat.meatspac.es!

    My team mate Edna Piranha is not only an awesome hacker; she's also a fantastic philosopher! Communication and online interactions is a subject that has kept her mind busy for a long time, and it has also resulted in a bunch of interesting experimental projects...

Incredible Demos

Discussion

  1. Chris Zuber

    Initializing with 0 might not be necessary since it takes the value from the first item in the array if not provided (and then skips the first item for the rest). It’s very slightly slower to set it to 0.

    Here’s what I wonder though… Suppose this were in some math.js module. Would it be sum(nums) or sum(...nums)? sum([1,2,3]) or sum(1,2,3)? I kinda prefer the latter.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!