parseInt and Radix

By  on  

Everyone knows that the parseInt function within JavaScript turns your decimal number or string into a rounded integer.  parseInt turns 10.937 into 10, 0.2 into 0, and "someValue" into NaN.  If you use parseInt without a radix, however, you'll receive a warning that no radix has been provided.  In most cases, the radix you want to use is 10:

parseInt(10.83, 10); // 10, no warning
parseInt(.83, 10); // 0, no warning

parseInt(0.8); // 8, unintended result
parseInt(0.8, 10); // 0, intended result

Using a 10 radix means the number is parsed with a base 10 and thus turns the number into the integer you're expecting, without the annoying warning.  The radix is important if you're need to guarantee accuracy with variable input (basic number, binary, etc.).  For best results, always use a radix of 10!

Recent Features

  • By
    Create Namespaced Classes with MooTools

    MooTools has always gotten a bit of grief for not inherently using and standardizing namespaced-based JavaScript classes like the Dojo Toolkit does.  Many developers create their classes as globals which is generally frowned up.  I mostly disagree with that stance, but each to their own.  In any event...

  • By
    5 Ways that CSS and JavaScript Interact That You May Not Know About

    CSS and JavaScript:  the lines seemingly get blurred by each browser release.  They have always done a very different job but in the end they are both front-end technologies so they need do need to work closely.  We have our .js files and our .css, but...

Incredible Demos

  • By
    Drag and Drop MooTools File Uploads

    Honesty hour confession:  file uploading within the web browser sucks.  It just does.  Like the ugly SELECT element, the file input is almost unstylable and looks different on different platforms.  Add to those criticism the fact that we're all used to drag and drop operations...

  • By
    CSS Fixed Positioning

    When you want to keep an element in the same spot in the viewport no matter where on the page the user is, CSS's fixed-positioning functionality is what you need. The CSS Above we set our element 2% from both the top and right hand side of the...

Discussion

  1. Nice!!!@

  2. whoever

    It’s especially important when you convert strings like ‘010’ for instance :).

  3. MaxArt

    It may be that I rarely use parseInt, but where’s this warning you’re talking about?
    I can’t see it in the console.

  4. xadet

    @MaxArt jshint and jslint display the warnings, not the console.

    • MaxArt

      Aahh, JSLint, ok.
      Maybe that’s because it’s an instrument of the Devil.

  5. “Everyone knows that the parseInt function within JavaScript turns your decimal number into a rounded integer”
    In reality parseInt turns your strings into rounded integers. I think decimals are cast to strings and then integers when calling this function. To turn decimals into integers there are Math.round / Math.ceil / Math.floor

    Also, parseInt(0.8) returns 0 in the latest Chrome and Firefox.

    All these quick beginners code tips you have been posting lately… is that because of lack of sleep / time due to fatherhood?

  6. parseInt will turn “someValue” to NaN, not 0

  7. Om Shankar

    Nice catch.
    However, I didn’t expect it on your site, as this is a very basic thing put in “Number” sections of many JS Primer Books

  8. A minor point: 10.937 to 10 is not rounding. Perhaps you meant “whole number” not “rounded number”?

  9. 新設する原案もまとめた プラダ 財布 公式。

  10. e cigarette… e cigarette, electronic cigarette review, best electronic cigarette e cig! e cig! electronic cigarette! e cigarettes ecig! e cigarette electronic cigarettes… electronic cigarette reviews? e cigarette electronic cigarette reviews best electronic cigarette. electronic cigarette reviews electronic cigarette… electronic cigarettes best electronic cigarette,

  11. Peter Ho

    I tried on IE10, firefox and chrome, I don’t see the problem. parseInt(“0.8”) returns 0.

  12. Peter : jsLint say “Missing radix parameter” if you don’t set it

  13. The radix is really annoying. If I know the string it an int (from the GUI, say), I just use parseFloat(str).

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