The Number.parseInt() method parses a string argument and returns an integer of the specified radix or base.


Number.parseInt(string, radix)



The value to parse. If this argument is not a string, then it is converted to one using the ToString abstract operation. Leading whitespace in this argument is ignored.

radix_ Optional_

An integer between 2 and 36 that represents the radix (the base in mathematical numeral systems) of the string.

If radix is undefined or 0, it is assumed to be 10 except when the number begins with the code unit pairs 0x or 0X, in which case a radix of 16 is assumed.

Return value

An integer parsed from the given string.

If the radix is smaller than 2 or bigger than 36, or the first non-whitespace character cannot be converted to a number, NaN is returned.


if (Number.parseInt === undefined) {
    Number.parseInt = window.parseInt


Number.parseInt vs parseInt

This method has the same functionality as the global parseInt() function:

Number.parseInt === parseInt // true

and is part of ECMAScript 2015 (its purpose is modularization of globals). Please see parseInt() for more detail and examples.


ECMAScript Language Specification (ECMAScript)
# sec-number.parseint

Browser compatibility

BCD tables only load in the browser

See also

  • A polyfill of Number.parseInt is available in core-js
  • The Number object it belongs to.
  • The global parseInt() method.