TheMath.fround() static method returns the nearest32-bit single precision float representation of a number.

Try it

console.log(Math.fround(5.5));// Expected output: 5.5console.log(Math.fround(5.05));// Expected output: 5.050000190734863console.log(Math.fround(5));// Expected output: 5console.log(Math.fround(-5.05));// Expected output: -5.050000190734863

Syntax

Math.fround(doubleFloat)

Parameters

doubleFloat

A number.

Return value

The nearest32-bit single precision float representation ofdoubleFloat.

Description

JavaScript uses 64-bit double floating-point numbers internally, which offer a very high precision. However, sometimes you may be working with 32-bit floating-point numbers, for example if you are reading values from aFloat32Array. This can create confusion: checking a 64-bit float and a 32-bit float for equality may fail even though the numbers are seemingly identical.

To solve this,Math.fround() can be used to cast the 64-bit float to a 32-bit float. Internally, JavaScript continues to treat the number as a 64-bit float, it just performs a "round to even" on the 23rd bit of the mantissa, and sets all following mantissa bits to0. If the number is outside the range of a 32-bit float,Infinity or-Infinity is returned.

Becausefround() is a static method ofMath, you always use it asMath.fround(), rather than as a method of aMath object you created (Math is not a constructor).

Examples

Using Math.fround()

The number 1.5 can be precisely represented in the binary numeral system, and is identical in 32-bit and 64-bit:

Math.fround(1.5); // 1.5Math.fround(1.5) === 1.5; // true

However, the number 1.337 cannot be precisely represented in the binary numeral system, so it differs in 32-bit and 64-bit:

Math.fround(1.337); // 1.3370000123977661Math.fround(1.337) === 1.337; // false

$2^{150}$ is too big for a 32-bit float, soInfinity is returned:

2 ** 150; // 1.42724769270596e+45Math.fround(2 ** 150); // Infinity

Specifications

Browser compatibility

See also

• Polyfill ofMath.fround incore-js
• es-shims polyfill ofMath.fround
• Math.round()