gistfile1.js

var inject = function(iterable, initial, func) {
	var cur = initial
	for(var i = 0;i < iterable.length;i++) {
		cur = func(cur, iterable[i])
	}
	return cur
}

var map = function(arr, func) {
	return inject(arr, [], function(memo, val) {
		memo.push(func(val))
		return memo
	})
}

map([1,2,3], function(x) { return x + 1 }) // #=> [2,3,4]