what is stack in js code example

Example: stack in javascript

class Stack{
   constructor() 
    { 
        this.items = []; 
    } 
   
    push(element) 
   { 
    // push element into the items 
    this.items.push(element); 
    }
  
    pop() 
    { 
    if (this.items.length == 0) 
        return "Underflow"; 
    return this.items.pop(); 
    } 
  
    peek() 
	{ 
    	return this.items[this.items.length - 1]; 
	} 
  
    printStack() 
    { 
    	var str = ""; 
    	for (var i = 0; i < this.items.length; i++) 
        	str += this.items[i] + " "; 
    	return str; 
    } 

}