Math.cbrt()

The Math.cbrt() function returns the cube root of a number, that is

$$\mathtt{Math.cbrt(x)} = \sqrt[3]{x} = \text{the unique} \; y \; \text{such that} \; y^3 = x$$

Math.cbrt(x)

x

A number.

The cube root of the given number.

Because cbrt() is a static method of Math, you always use it as Math.cbrt(), rather than as a method of a Math object you created (Math is not a constructor).

For all $x \geq 0$, have $\sqrt[3]{x} = x^{1/3}$ so this can be emulated by the following function:

if (!Math.cbrt) {
  Math.cbrt = (function(pow) {
    return function cbrt(x){
      // ensure negative numbers remain negative:
      return x < 0 ? -pow(-x, 1/3) : pow(x, 1/3);
    };
  })(Math.pow); // localize Math.pow to increase efficiency
}

Math.cbrt(NaN); // NaN
Math.cbrt(-1); // -1
Math.cbrt(-0); // -0
Math.cbrt(-Infinity); // -Infinity
Math.cbrt(0); // 0
Math.cbrt(1); // 1
Math.cbrt(Infinity); // Infinity
Math.cbrt(null); // 0
Math.cbrt(2);  // 1.2599210498948732

• Math.pow()
• Math.sqrt()