Concatenate n-many ArrayBuffers

concat.array.buffers.js

/**
 * Concatenates n-many ArrayBuffers
 * Based on the https://gist.github.com/72lions/4528834
 *
 * @param {...ArrayBuffer} ArrayBuffer(s) to concatenate
 * @return {ArrayBuffer} The new ArrayBuffer created out of n buffers.
 */
var concatArrayBuffers = function () {
    var buffers = Array.prototype.slice.call(arguments),
        buffersLengths = buffers.map(function(b) { return b.byteLength; }),
        totalBufferlength = buffersLengths.reduce(function(p, c) { return p+c; }, 0),
        unit8Arr = new Uint8Array(totalBufferlength);
    buffersLengths.reduce(function (p, c, i) {
        unit8Arr.set(new Uint8Array(buffers[i]), p);
        return p+c;
    }, 0);
    return unit8Arr.buffer;
};
// To call it:
// concatArrayBuffers.apply(this/context, [ArrayBuffers]);

respectfully, i offer this slight modification, to allow mixed type arrays or buffers to be concatenated on arbritrary byte boundaries

function concatArrayBuffers () {
        var buffers = Array.prototype.slice.call(arguments).map(function(ab){
               if (ab.constructor===ArrayBuffer) return ab;
               return new Uint8Array(ab.buffer.slice(ab.byteOffset,ab.byteLength)).buffer; 
            }),
            buffersLengths = buffers.map(function(b) { return b.byteLength; }),
            totalBufferlength = buffersLengths.reduce(function(p, c) { return p+c; }, 0),
            unit8Arr = new Uint8Array(totalBufferlength);
        buffersLengths.reduce(function (p, c, i) {
            unit8Arr.set(new Uint8Array(buffers[i]), p);
            return p+c;
        }, 0);
        return unit8Arr.buffer;
    }