Fake TypedArray

setupTypedArray.js

    function setupTypedArray(name) {
        var fake_typedarray;

        if (name in window) {
            return window[name];
        }

        console.warn(name + ' is not defined, so use fake.');
        fake_typedarray = function(arg) {
            var i;

            if (typeof arg === 'number' && arg > 0) {
                arg >>= 0;
                this.length = arg;
                while (arg--) {
                    this[arg] = 0;
                }
            } else if (arg instanceof Array) {
                for (i = arg.length; i--;) {
                    this[i] = arg[i];
                }
                this.length = arg.length;
            } else {
                this.length = 0;
            }
        };

        fake_typedarray.prototype.set = function(array, offset) {
            var i, j, jmax;
            offset = (offset || 0) >> 0;
            for (i = offset, j = 0, jmax = array.length; j < jmax; i++, j++) {
                this[i] = array[j];
            }
        };

        fake_typedarray.prototype.subarray = function(begin, end) {
            var i, j, result = new fake_typedarray();
            if (begin < end) {
                for (i = 0, j = begin; j < end; i++, j++) {
                    result[i] = this[j];
                }
                result.length = end - begin;
            }
            return result;
        };
        return fake_typedarray;
    }

    var Float32Array = setupTypedArray("Float32Array");

    var f0 = new Float32Array(3);                //  0  0  0  x  x
    var f1 = new Float32Array([10, 20]);         // 10 20  x  x  x
    var f2 = new Float32Array(5); f2.set(f1, 2); //  0  0 10 20  0
    var f3 = f2.subarray(2, 5);                  // 10 20  0  x  x
    console.log('f0=', f0[0], f0[1], f0[2], f0[3], f0[4]);
    console.log('f1=', f1[0], f1[1], f1[2], f1[3], f1[4]);
    console.log('f2=', f2[0], f2[1], f2[2], f2[3], f2[4]);
    console.log('f3=', f3[0], f3[1], f3[2], f3[3], f3[4]);