Input valueAsNumber

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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!

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Discussion

  1. Martin

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

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