How to dominate Javascript's world

extensions.js

(function extensions() {

	function arr(val) {
		return Array.prototype.slice.call(val);
	}

	function extend(Type, prototype) {
		function E(val) { this.val = val }
		E.prototype = prototype;
		prototype.constructor = E;
		Type.prototype.ext = function() { return new E(this) };
	}


	extend(Function, {
		bindArgs: function(var_args) {
			var self = this;
			var binded = arr(arguments);
			return function() {
				return self.apply(this, binded.concat(arr(arguments)));
			};
		},

		bindArg: function(index, value) {
			var self = this;
			return function() {
				var args = arr(arguments);
				args.splice(index, 0, value);
				return self.apply(this, args);
			};
		},

		rest: function(from) {
			from = from || 0;
			var self = this;
			return function() {
				var args = arr(arguments);
				if (from === 0)
					return self.call(this, args);

				var result = args.splice(0, from);
				result.push(args.splice(from);
				return self.apply(this, result);
			};
		}
	});


	extend(String, {
		startsWith: function(start) {
			return this.val.substr(0, start.length) === start;
		},

		endsWith: function(end) {
			return this.val.substr(-end.length) === end;
		},

		repeat: function(times, separator) {
			var result = [];
			for (var i = times; i--; )
				result[i] = this.val;
			return result.join(separator || '');
		}
	});


	extend(Object, {
		each: function(args) {
			args.shift(this.val);
			return _.each.apply(_, args);
		}.ext().rest(),
	});


	extend(Array, {
		first: function() {
			return this.val.length ? this.val[0] : null;
		},

		last: function() {
			return this.val.length ? this.val[this.val.length - 1] : null;
		}
	});


})();