string-v8.js

// this will optimize-deoptimize leading to v8 giving
// up on the function
String.prototype.hashCode = function() {
  var n = this.length;
  var hash = 0;

  if(n != 0) {
    for(var i = 0; i < n; ++i)
      hash = Math.imul(31, hash) + this.charCodeAt(i) | 0;
    return hash;
  }

  return 0;
};

// this works just fine
function hashCode(s) {
  var n = s.length;
  var hash = 0;

  if(n != 0) {
    for(var i = 0; i < n; ++i)
      hash = Math.imul(31, hash) + s.charCodeAt(i) | 0;
    return hash;
  }

  return 0;
}

var n = 0;

for(var i = 0; i < 1000; ++i) {
  var s = "this is my string "+Math.round(Math.random()*1000.0)+" ...";
  n = n + s.hashCode() | 0;
  n = Math.imul(n, s.hashCode());
  //
  //n = n + hashCode(s) | 0;
  //n = Math.imul(n, hashCode(s));
}

print("n: "+n);