Fancy array construction (fully extendable)

Chain.js

function Chain (datum) {
    if (datum != undefined) {
        this.length = this.length !== undefined ? this.length + 1 : 1;
        
        this[this.length - 1] = datum;
        
        return Chain.bind(this);
    } else {
        return this;
    }
};

Chain.prototype = Array.prototype;

example.js

var chain = new Chain("string")(33)(function getItem(i) {
  // `this` is bound as chain.data
  return this[i];
})();

console.log(chain);
// => ["string", 33, function function]

console.log(chain[2](1));
// => 33

chain.forEach(function(link) {
  console.log(link);
});
// => string
//    33
//    function getItem(i) { ...