JavaScript parseFloat() function explained with examples

Posted on Mar 07, 2022

Learn how to create a floating-point number using parseFloat() in JavaScript

The JavaScript parseFloat() function is a built-in function that returns a floating-point number from the given string argument.

The function allows you to extract a number from a string as shown below:

console.log(parseFloat("12.57.a ")); // 12.57

When a number can’t be parsed from the argument, a NaN will be returned by the function:

console.log(parseFloat("abc ")); // NaN

The parseFloat() function can’t adjust the number of digits for the decimal point.

When you need a certain amount of decimal point digits, you need to use the toFixed() method.

See also: Rounding numbers with toFixed() method

For example, suppose you only want 2 decimal point digits out of the string number. Here’s how you do it:

let string = "37.5930"
let float = parseFloat(string);
let fixedFloatString = float.toFixed(2); // "37.59"
let fixedFloat = parseFloat(fixedFloatString);

console.log(fixedFloat); // 37.59

The parseFloat() function is called two times because the toFixed() method returns a string representing the number where you call the function from.

If you don’t need a number type representation of the number, you can omit the last parseFloat() function call.

Use isNaN() to check the returned value of parseFloat()

Finally, the parseFloat() function returns a NaN when the given argument has no valid number representation.

Since a NaN isn’t a useful value, you might want to replace it with 0 in some cases.

Consider the following example code:

function multiplyByTwo(x) {
  if (isNaN(parseFloat(x))) {
    x = 0
  return parseFloat(x) * 2;

console.log(multiplyByTwo("abc")) // 0

console.log(multiplyByTwo("3.21`")) // 6.42

When the value of parseFloat(x) is NaN, the x variable will be replaced with 0 instead.

This way, the calculation of parseFloat(x) * 2 will always return a number 0 in place of NaN.

Now you’ve learned how the parseFloat() function works in JavaScript. Good work! 😉

Level up your programming skills

I'm sending out an occasional email with the latest programming tutorials. Drop your email in the box below and I'll send new stuff straight into your inbox!

No spam. Unsubscribe anytime.