var a = new Uint8Array([0x12, 0x34]);
var b = new Uint16Array(a.buffer);
alert("0x" + (b[0]).toString(16)); // #=> 0x3412 or 0x1234 ?
The following buffer is created:

Uint16Array, Uint32Array, Int16Array, and Int32Array (JavaScript Typed Array) seem to use native endian. If you use little endian machine (e.g. x86, x64), b[0] is 0x3412. If you use big endian machine (e.g. Sun SPARC, PowerPC), b[0] is 0x1234. (But I did not check since I have no big endian machine.)

See also