Popular:
 Building Resilient Systems on AWS: Learn how to design and implement a resilient, highly available, fault-tolerant infrastructure on AWS.

Type Conversion with JavaScript Arrays

By  on  

JavaScript's loose nature allows developers to employ amazing tricks to do just about anything you'd like. I've detailed how you can filter falsy values in arrays using a filter(Boolean) trick, but reader David Hibshman shared another trick for typecasting array values the same way.

To typecast an array of elements, you can use map and the desired return type:

["1", "9", "-9", "0.003", "yes"].map(Number);
// [1, 9, -9, 0.003, NaN]

I love this trick but you could argue the code itself could be considered confusing, so wrapping it a helper function would be helpful:

function arrToNumber(arr) {
  return arr.map(Number).filter(Boolean);
}

Validation could and should probably be more rigorous but basic validation through typecasting might help you!

Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring
Request Metrics real user monitoring

Recent Features

  • By
    Chris Coyier’s Favorite CodePen Demos

    David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

  • By
    Vibration API

    Many of the new APIs provided to us by browser vendors are more targeted toward the mobile user than the desktop user.  One of those simple APIs the Vibration API.  The Vibration API allows developers to direct the device, using JavaScript, to vibrate in...

Incredible Demos

  • By
    Modal-Style Text Selection with Fokus

    Every once in a while I find a tiny JavaScript library that does something very specific, very well.  My latest find, Fokus, is a utility that listens for text selection within the page, and when such an event occurs, shows a beautiful modal dialog in...

  • By
    iPad Detection Using JavaScript or PHP

    The hottest device out there right now seems to be the iPad. iPad this, iPad that, iPod your mom. I'm underwhelmed with the device but that doesn't mean I shouldn't try to account for such devices on the websites I create. In Apple's...

Discussion

  1. jzrskc
    ["0", "9", "-9", "0.003", "yes", true, false, undefined, null].map(Number);
// [0, 9, -9, 0.003, NaN, 1, 0, NaN, 0]

["0", "9", "-9", "0.003", "yes", true, false, undefined, null].map(parseFloat)
// [0, 9, -9, 0.003, NaN, NaN, NaN, NaN, NaN]
  2. MKM

    The .filter(Boolean) part also sees the zeros as booleans and removes those numbers.

  3. BryanYang

    very useful!

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