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
    Conquering Impostor Syndrome

    Two years ago I documented my struggles with Imposter Syndrome and the response was immense.  I received messages of support and commiseration from new web developers, veteran engineers, and even persons of all experience levels in other professions.  I've even caught myself reading the post...

  • By
    Regular Expressions for the Rest of Us

    Sooner or later you'll run across a regular expression. With their cryptic syntax, confusing documentation and massive learning curve, most developers settle for copying and pasting them from StackOverflow and hoping they work. But what if you could decode regular expressions and harness their power? In...

Incredible Demos

  • By
    MooTools Text Flipping

    There are lots and lots of useless but fun JavaScript techniques out there. This is another one of them. One popular April Fools joke I quickly got tired of was websites transforming their text upside down. I found a jQuery Plugin by Paul...

  • By
    Scrolling “Go To Top” Link Using Dojo

    One of the most popular code snippets of posted on my blog has been the scrolling "Go To Top" link snippet. The premise of the snippet is simple: once the user scrolls an element (usually the BODY element) past a given threshold, a "Go...

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!