Vanilla JavaScript String to Number

Vanilla JavaScript String to Number

Chris Bongers
·Aug 4, 2020·

2 min read

Sometimes we want to convert a number to a string; in my latest code piece, there was a limit set on a data attribute. This comes true as a string, so how do we convert this to a number in JavaScript?

In this case, there is not one but three valid and supported methods of converting our string to a number.

  • Number
  • parseInt
  • parseFloat

JavaScript Number Method

Number is a generic way of converting. It's actually the more stricter check here are some examples with outputs:

<!-- Number -->
console.log(Number(`1337`)); // 1337
console.log(Number(`13.37`)); // 13.37
console.log(Number(`13leet37`)); // NaN
console.log(Number(`13,37`)); // NaN

As you can see it works on actual numbers, but as soon as we use other characters or a comma it won't work.

JavaScript ParseInt Method

ParseInt converts our string into an integer non rounded. It has two arguments, the input and the radix which is the base number. For us the default is 10

<!-- ParseInt -->
var text1 = '1337';
var text2 = '13.37';
var text3 = '13leet37';
var text4 = '13,37';
console.log(parseInt(text1, 10)); // 1337
console.log(parseInt(text2, 10)); // 13
console.log(parseInt(text3, 10)); // 13
console.log(parseInt(text4, 10)); // 13

The downside can be it's rounding everything, so let's look at ParseFloat.

JavaScript ParseFloat Method

As mentioned the parseFloat is used to return stuff with decimals.

<!-- ParseFloat -->
var text1 = '1337';
var text2 = '13.37';
var text3 = '13.3leet37';
var text4 = '13,37';
console.log(parseFloat(text1, 10)); // 13.37
console.log(parseFloat(text2, 10)); // 13
console.log(parseFloat(text3, 10)); // 13.3
console.log(parseFloat(text4, 10)); // 13

Very cool method!

See all these in action on Codepen.

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