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    Math.imul()

    This is an experimental technology, part of the ECMAScript 6 (Harmony) proposal.
    Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future version of browsers as the spec changes.

    Summary

    The Math.imul() function returns the result of the C-like 32-bit multiplication of the two parameters.

    Syntax

    Math.imul(a, b)

    Parameters

    a
    First number.
    b
    Second number.

    Description

    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).

    Examples

    Example: Using 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
    

    Polyfill

    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);
    };
    

    Specifications

    Specification Status Comment
    ECMAScript 6 (ECMA-262)
    The definition of 'Math.imul' in that specification.
    Release Candidate Initial definition.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support 28 20 (20) ? 16 7
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support ? ? 20.0 (20) ? ? iOS 7

    Document Tags and Contributors

    Last updated by: Mingun,