Input valueAsNumber

By  on  

Every once in a while I learn about a JavaScript property that I wish I had known about years earlier -- valueAsNumber is one of them. The valueAsNumber provides the value of an input[type=number] as a Number type, instead of the traditional string representation when you get the value:

/*
 Assuming an <input type="number" value="1.234" />
*/

// BAD: Get the value and convert the number
input.value // "1.234"
const numberValue = parseFloat(input.value, 10);

// GOOD: Use valueAsNumber
input.valueAsNumber // 1.234

This property allows us to avoid parseInt/parseFloat, but one gotcha with valueAsNumber is that it will return NaN if the input is empty.

Thank you to Steve Sewell for making me aware of valueAsNumber!

Recent Features

Incredible Demos

  • By
    MooTools Image Preloading with Progress Bar

    The idea of image preloading has been around since the dawn of the internet. When we didn't have all the fancy stuff we use now, we were forced to use ugly mouseover images to show dynamism. I don't think you were declared an official...

  • By
    MooTools 1.3 Browser Object

    MooTools 1.3 was just released and one of the big additions is the Browser object.  The Browser object is very helpful in that not only do you get information about browser type and browser versions, you can gain information about the user's OS, browser plugins, and...

Discussion

  1. Martin

    Great tip! Is there anything wrong with parseInt / parseFloat, apart from the extra line of code? (you labeled it “BAD”)

    • Kyryl

      Depending on lang, decimal separator can be comma. So, parseFloat('0,01'); will return 0 instead of 0.01.

  2. yann

    Leaving this here hoping it saves some time I wish I had saved to some other person looking for an answer…

    If you’re using this on an html input, maybe with angular… it works great, but you NEED to add the 'type="number"' to your input or it will keep giving u NaN no matter what’s in the input box.

    The reason ?
    for some reason that I am not looking up at this time, valueAsNumber does NOT work on String types, but the default type of an html input is String.

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