Proof of concept for adding type-hinting to JavaScript.

TypeHint.js

// Set testable values;
window.Type = {
	Number: 1,
	String: 'a',
	Function: function(){}
}

// Add a hint method;
Function.prototype.hint = function(){

	var tArgs = Array.prototype.slice.call(arguments, 0),
		tFunc = this;

	return function(){

		// Convert arguments to an array.
		var lArgs = Array.prototype.slice.call(arguments);

		// Make sure all arguments where supplied
		if ( lArgs.length !== tArgs.length ) {
			throw new Error("Fail,arglength");
		}

		// Validate all argument types.
		tArgs.forEach(function(a,i){
			if ( typeof lArgs[i] !== typeof a ){
				throw new Error("Fail,argtype");
			}
		});

		// Call the initial function.
		tFunc.apply(this, lArgs);
	};
};

usage.js

var cake = function( a, b, c ){

// This function will only be called if a is a number,
// b is a string and c is a function.

}.hint( Type.Number, Type.String, Type.Function );

cake( 3, 'Hello World!', function(){} );
cake( 'Hello World!', 4, function(){} ); // Will fail!