The Math.imul()
function returns the result of the C-like 32-bit multiplication of the two parameters.
Math.imul(a, b)
a
b
Math.imul()
allows for fast 32-bit integer multiplication with C-like semantics. This feature is useful for projects like Emscripten. Because imul()
is a static method of Math
, you always use it as Math.imul()
, rather than as a method of a Math
object you created (Math
is not a constructor).
Math.imul()
Math.imul(2, 4); // 8 Math.imul(-1, 8); // -8 Math.imul(-2, -2); // 4 Math.imul(0xffffffff, 5); // -5 Math.imul(0xfffffffe, 5); // -10
This can be emulated with the following function:
Math.imul = Math.imul || function(a, b) { var ah = (a >>> 16) & 0xffff; var al = a & 0xffff; var bh = (b >>> 16) & 0xffff; var bl = b & 0xffff; // the shift by 0 fixes the sign on the high part // the final |0 converts the unsigned value into a signed value return ((al * bl) + (((ah * bl + al * bh) << 16) >>> 0)|0); };
Created by Mozilla Contributors, license: CC-BY-SA 2.5