stack in javascript

1class Stack{
2   constructor() 
3    { 
4        this.items = []; 
5    } 
6   
7    push(element) 
8   { 
9    // push element into the items 
10    this.items.push(element); 
11    }
12  
13    pop() 
14    { 
15    if (this.items.length == 0) 
16        return "Underflow"; 
17    return this.items.pop(); 
18    } 
19  
20    peek() 
21	{ 
22    	return this.items[this.items.length - 1]; 
23	} 
24  
25    printStack() 
26    { 
27    	var str = ""; 
28    	for (var i = 0; i < this.items.length; i++) 
29        	str += this.items[i] + " "; 
30    	return str; 
31    } 
32
33}

1function Stack() {
2  var collection = [];
3  this.print = function() {
4    console.log(collection);
5  };
6  this.push = function(val) {
7    return collection.push(val);
8  };
9  this.pop = function() {
10    return collection.pop();
11  };
12  this.peek = function() {
13    return collection[collection.length - 1];
14  };
15  this.isEmpty = function() {
16    return collection.length === 0;
17  };
18  this.clear = function() {
19    collection.length = 0;
20  };
21}
22