The Number.parseFloat() static method parses an argument and returns a floating point number. If a number cannot be parsed from the argument, it returns NaN.

Try it

function circumference(r) {
  if (Number.isNaN(Number.parseFloat(r))) {
    return 0;
  }
  return parseFloat(r) * 2.0 * Math.PI;
}

console.log(circumference("4.567abcdefgh"));
// Expected output: 28.695307297889173

console.log(circumference("abcdefgh"));
// Expected output: 0

Syntax

Number.parseFloat(string)

Parameters

string

The value to parse, coerced to a string. Leading whitespace in this argument is ignored.

Return value

A floating point number parsed from the given string.

Or NaN when the first non-whitespace character cannot be converted to a number.

Examples

Number.parseFloat vs. parseFloat

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

Number.parseFloat === parseFloat; // true

Its purpose is modularization of globals.

See parseFloat() for more detail and examples.

Specifications

Browser compatibility

See also

• Polyfill of Number.parseFloat in core-js
• es-shims polyfill of Number.parseFloat
• Number
• parseFloat()