Extending Object and Array and the unexpected results in looping

object-array-loop-fail.js

/**
 * Object/Array native objects being extended via prototype produces unexpected results when 
 * when looping through objects/arrays respectively.  
 * @author  Rob MacInnis
 * @see  http://stackoverflow.com/questions/10695506/adding-function-to-object-prototype-causes-function-to-show-up-in-all-for-x-in
 */

require('colors'); 

// Extending a native JS object
Array.prototype.foo = function(i) {
	return i + 1; 
}; 

Array.prototype.bar = 'bar'; 

// Doesn't show up 
Array.baz = 'baz'; 

var a = new Array(); 

// console.log(a.foo(1)); // 2

// The `foo` function shows up in the Array.__proto__
// affecting the usage of arrays henceforth
var a1 = [1,2,3]; 

console.log('-----------------'.blue); 
console.log('Test 1.1: Array looping shows functions added via prototype'.blue); 
console.log('-----------------'.blue); 

for(var i in a1) {
	console.log('Key'.green, i, 'Val'.green, a1[i]); // 0, 1, 2, 3, foo <-- shouldn't be there 
}

console.log('-----------------'); 
console.log('Test 1.2: Using current Array hasOwnProperty to filter results'); 
console.log('-----------------'); 

for(var i in a1) {
	if(a1.hasOwnProperty(i)) {
		console.log('Key', i, 'Val', a1[i]); 
	}
}

console.log('-----------------'.blue); 
console.log('Test 2.1: Object looping contains prototype function'.blue); 
console.log('-----------------'.blue); 

Object.prototype.bar = function() {
	return 'bar'; 
};

var b = new Object(); 

var b1 = { baz: 'quux' };  

for(var i in b1) {
	console.log('Key'.green, i, 'Val'.green, b1[i]); // bar
}

console.log('-----------------'.blue); 
console.log('Test 2.2: Using current object hasOwnProperty to filter results'.blue); 
console.log('-----------------'.blue); 

for(var i in b1) {

	if(b1.hasOwnProperty(i)) {
		console.log('Key'.green, i, 'Val'.green, b1[i]); 
	}
	// if(Object.prototype.hasOwnProperty(i)) {
	// 	console.log('Key', i, 'Val', b1[i]); 
	// }
}


/**
 * -----------------
 * Test 1.1: Array looping shows functions added via prototype
 * -----------------
 * Key 0 Val 1
 * Key 1 Val 2
 * Key 2 Val 3
 * Key foo Val function (i) {
 * 	return i + 1;
 * }
 * Key bar Val bar
 * -----------------
 * Test 1.2: Using current Array hasOwnProperty to filter results
 * -----------------
 * Key 0 Val 1
 * Key 1 Val 2
 * Key 2 Val 3
 * -----------------
 * Test 2.1: Object looping contains prototype function
 * -----------------
 * Key baz Val quux
 * Key bar Val function () {
 * 	return 'bar';
 * }
 * -----------------
 * Test 2.2: Using current object hasOwnProperty to filter results
 * -----------------
 * Key baz Val quux
 */