How to speed up checksum computations of a string?

Wow, thanks! it's great to see the benchmarks for this. If I'm honest it's a surprise that cks is better than cks4. It's been a real struggle to find anything that's faster, but:

// just removing whitespace from the cks callback gives you a tiny bit
function cks9(m) {
  var s = 0;
  new Uint8Array(E.toArrayBuffer(m)).forEach(f­unction (c) {s^=c});
  return s;
}
// and pre-binding the function and using a for in loop helps a surprising amount
function cks10(m) { 
  var s = 0;
  var c = m.charCodeAt.bind(m);
  for (var i in m)s^=c(i);
  return s;
}

But you should be able to use compiled, for instance try:

function xor(a,b) { "compiled"; return a^b; }
function cks5(m) {
  return new Uint8Array(E.toArrayBuffer(m)).reduce(xo­r, 0);
}
function cks6(m) { 
  "compiled"; 
  var ck = 0;
  var l = 0|m.length;
  for (var i=0;i<l;i++) ck ^= m.charCodeAt(i);
  return ck;
}
function cks7(m) { 
  "compiled"; 
  var ck = 0;
  var l = 0|m.length; // ensure we don't have to check the length each time
  var c = m.charCodeAt.bind(m); // ensure we don't have to look up 'charCodeAt' each time
  for (var i=0;i<l;i++) ck ^= c(i);
  return ck;
}

I just had a quick play and they seem to be 2x or more faster than cks10 (especially the last one). Hope that helps!