The Math.fround()
function returns the nearest 32-bit single precision float representation of a Number
.
Math.fround()
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Syntax
Math.fround(doubleFloat)
Parameters
Return value
The nearest 32-bit single precision float representation of the given number.
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 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).
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); // 1.5 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
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
Specifications
Specification |
---|
ECMAScript Language Specification # sec-math.fround |
Browser compatibility
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
|
See also
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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/fround