Overload a function according to the types of arguments passed in

overload-by-type.js

// Overload a function according to the types of arguments passed in:
// 
// var fn = overloadByTypes({
//     'object': function(object) {},
//     'string number': function(string, number) {},
//     'default': function() {} 
// });
// 
// Returns the result of the called function. To return this to create
// a chainable method, for example, pass in true as a second argument:
// 
// var fn = overloadByTypes({...}, true);

function toType(object) {
	return typeof object;
}

function overloadByTypes(signatures, returnFlag) {
	return function method() {
		var signature = Array.prototype.map.call(arguments, toType).join(' ');
		var fn = signatures[signature] || signatures.default;

		if (!fn) { throw new Error('overloadByTypes: No function for type signature "' + signature + '" and no "default" defined.'); }

		var result = fn.apply(this, arguments);
		return returnFlag ? this : result ;
	};
}