SO 8609289

gistfile1.js

var buf1 = new Buffer(1024);
for (var i = 0; i < 1024; i++) {
	buf1[i] = i
}


function toArrayBuffer(buffer) {
    var ab = new ArrayBuffer(buffer.length);
    var view = new Uint8Array(ab);
    for (var i = 0; i < buffer.length; ++i) {
        view[i] = buffer[i];
    }
    return ab;
}

function toArrayBufferViaReads(buffer) {
	// Unsafely assumes buffer size is a multiple of 4
	var sizeofBuffer = buffer.length;
    var ab = new ArrayBuffer(sizeofBuffer);
    var view = new Uint32Array(ab);
    for (var srcI = destI = 0; srcI < sizeofBuffer; srcI += 4, destI++) {
        view[destI] = buffer.readUInt32LE(srcI);
    }
    return ab;
}

times are ms to run 15,000 times (lower is better)

> for(var tt=0;tt<20;tt++){
  console.time("bytewise");
  for(var t=0;t<15000;t++){
    toArrayBufferViaReads(buf1)
  };
  console.timeEnd("bytewise")
}

sample	bytewise	viaReads
1	267	473
2	234	421
3	218	421
4	234	390
5	219	437
6	234	437
7	249	426
8	219	421
9	234	422
10	223	436
11	239	422
12	255	421
13	223	423
14	250	442
15	221	406
16	236	405
17	234	453
18	234	424
19	250	421
20	234	421
mean	235.35	426.1