class Stack {
constructor() {
this.elements = [];
this.length = 0;
}
push(value) {
this.elements.push(value);
this.length++;
}
peek() {
return this.elements[this.length - 1];
}
pop() {
if(this.length === 0) {
return null;
}
this.length--;
return this.elements.pop();
}
isEmpty() {
return (this.length === 0) ? true : false;
}
}
const stack = new Stack();
stack.push(1);
stack.push(2);
stack.push(3);
console.log(stack);
console.log(stack.pop());
console.log(stack.pop());
console.log(stack.peek());
console.log(stack.isEmpty());
console.log(stack.pop());
console.log(stack.isEmpty());
console.log(stack);
console.log(stack.pop());
