Data Structure: Stack

stack.js

class Stack {
  constructor() {
    this.stack = [];
  }
   
  get length() {
    return this.stack.length;
  }
  
  push(el) {
    this.stack.push(el);
  }
  
  pop() {
    return this.stack.pop()
  }
  
  peek() {
    if(this.isEmpty()) {
      return undefined
    }
    return this.stack[this.length - 1]
  }
  
  isEmpty() {
    return this.length === 0;
  }
}