CODE EXAMPLE FOR JAVASCRIPT

javascript fast inverse square root

function Q_rsqrt(number)
{ 
    var i;
    var x2, y;
    const threehalfs = 1.5;
  
    x2 = number * 0.5;
    y = number;
  
    var buf = new ArrayBuffer(4);
    (new Float32Array(buf))[0] = number;
    i = (new Uint32Array(buf))[0];
    i = (0x5f3759df - (i >> 1));
    (new Uint32Array(buf))[0] = i;
    y = (new Float32Array(buf))[0];
    y  = y * ( threehalfs - ( x2 * y * y ) );

    return y;
}