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
    5 HTML5 APIs You Didn’t Know Existed

    When you say or read "HTML5", you half expect exotic dancers and unicorns to walk into the room to the tune of "I'm Sexy and I Know It."  Can you blame us though?  We watched the fundamental APIs stagnate for so long that a basic feature...

  • By
    CSS 3D Folding Animation

    Google Plus provides loads of inspiration for front-end developers, especially when it comes to the CSS and JavaScript wonders they create. Last year I duplicated their incredible PhotoStack effect with both MooTools and pure CSS; this time I'm going to duplicate...

Incredible Demos

  • By
    Create a 3D Panorama Image with A-Frame

    In the five years I've been at Mozilla I've seen some awesome projects.  Some of them very popular, some of them very niche, but none of them has inspired me the way the MozVR team's work with WebVR and A-Frame project have. A-Frame is a community project...

  • By
    Implement jQuery’s hover() Method in MooTools

    jQuery offers a quick event shortcut method called hover that accepts two functions that represent mouseover and mouseout actions. Here's how to implement that for MooTools Elements. The MooTools JavaScript We implement hover() which accepts to functions; one will be called on mouseenter and the other...

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!