The Math.clz32() function returns the number of leading zero bits in the 32-bit binary representation of a number.
Math.clz32(x)x"clz32" is short for CountLeadingZeroes32.
If x is not a number, then it will be converted to a number first, then converted to a 32-bit unsigned integer.
If the converted 32-bit unsigned integer is 0, then return 32, because all bits are 0.
This function is particularly useful for systems that compile to JS, like Emscripten.
Math.clz32()Math.clz32(1); // 31
Math.clz32(1000); // 22
Math.clz32(); // 32
[NaN, Infinity, -Infinity, 0, -0, null, undefined, 'foo', {}, []].filter(
function(n) {
return Math.clz32(n) !== 32
}); // []
Math.clz32(true); // 31
Math.clz32(3.5); // 30
This polyfill depends on Math.imul.
Math.clz32 = Math.clz32 || (function () {
'use strict';
var table = [
32, 31, 0, 16, 0, 30, 3, 0, 15, 0, 0, 0, 29, 10, 2, 0,
0, 0, 12, 14, 21, 0, 19, 0, 0, 28, 0, 25, 0, 9, 1, 0,
17, 0, 4, , 0, 0, 11, 0, 13, 22, 20, 0, 26, 0, 0, 18,
5, 0, 0, 23, 0, 27, 0, 6, 0, 24, 7, 0, 8, 0, 0, 0]
// Adapted from an algorithm in Hacker's Delight, page 103.
return function (x) {
// Note that the variables may not necessarily be the same.
// 1. Let n = ToUint32(x).
var v = Number(x) >>> 0
// 2. Let p be the number of leading zero bits in the 32-bit binary representation of n.
v |= v >>> 1
v |= v >>> 2
v |= v >>> 4
v |= v >>> 8
v |= v >>> 16
v = table[Math.imul(v, 0x06EB14F9) >>> 26]
// Return p.
return v
}
})();
Created by Mozilla Contributors, license: CC-BY-SA 2.5