The `Math.fround()`

function returns the nearest 32-bit single precision float representation of a `Number`

.

The `Math.fround()`

function returns the nearest 32-bit single precision float representation of a `Number`

.

Math.fround(doubleFloat)

The nearest 32-bit single precision float representation of the given number.

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 a `Float32Array`

. 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 to `0`

. If the number is outside the range of a 32-bit float, `Infinity`

or `-Infinity`

is returned.

Because `fround()`

is a static method of `Math`

, you always use it as `Math.fround()`

, rather than as a method of a `Math`

object you created (`Math`

is not a constructor).

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); // 1.5 Math.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); // 1.3370000123977661 Math.fround(1.337) === 1.337; // false

$2^150$ is too big for a 32-bit float, so `Infinity`

is returned:

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

If the parameter cannot be converted to a number, or it is not-a-number (`NaN`

), `Math.fround()`

will return `NaN`

:

Math.fround('abc'); // NaN Math.fround(NaN); // NaN

Specification |
---|

ECMAScript Language Specification # sec-math.fround |

Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |

`fround` |
38 |
12 |
26 |
No |
25 |
8 |
38 |
38 |
26 |
25 |
8 |
3.0 |
1.0 |
0.12.0 |

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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/fround