find/find_if search utilities

gistfile1.js

Array.prototype.find_if = function(test, opts) {
  opts = opts || {};
  var key = opts.key || identity;
  var start = opts.start || 0;
  var end = opts.end || this.length;
  for (var i = 0; i < this.length; i++) {
    if (test(key(this[i]))) {
      return this[i];
    }
  }
  return null;
};

Array.prototype.find = function(match, opts) {
  opts = opts || {};
  var test = opts.test || function(x,y) { return x === y; };
  return this.find_if(function(x) { return test(match, x); }, opts);
};