Queue implemented in JS

queue.js

let Queue  = function(){
  this.Store = [];
}

Queue.prototype.enqueue  =  function(ele){
  this.Store.push(ele);
}

Queue.prototype.dequeue = function(){
  if(this.empty()){
    throw new Error("Queue is empty, you can't run the dequeue operation");
  }
  return this.Store.shift();
}

Queue.prototype.clear =  function(){
  this.Store = [];
  return true;
}

Queue.prototype.empty =  function(){
  if(this.Store.length == 0){
    return true;
  }

  return false;
}

Queue.prototype.toString = function(){
  let i = 0, 
    len = this.Store.length, 
    string = "";
  for(i; i < len; i++){
    string += this.Store[i] +  "\n" 
  }

  return string
}

Queue.prototype.front =  function(){
  if(this.empty()){
    throw new Error("Queue is empty");
  }

  return this.Store[0];
}

Queue.prototype.back =  function(){
  if(this.empty()){
    throw new Error("Queue is empty");
  }
  
  let len = this.Store.length, last = len - 1;
  return this.Store[last];
}


//============Using ES6 syntax============

class Queue  {
  constructor(){
    this.Store = [];
  }
  enqueue (ele){
    this.Store.push(ele);
  }

  dequeue(){
    if(this.empty()){
      throw new Error("Queue is empty, you can't run the dequeue operation");
    }
    return this.Store.shift();
  }

  clear(){
    this.Store = [];
    return true;
  }

  empty(){
    if(this.Store.length == 0){
      return true;
    }

    return false;
  }

  toString(){
    let i = 0,
      len = this.Store.length,
      string = "";
    for(i; i < len; i++){
      string += this.Store[i] +  "\n"
    }

    return string
  }

  front(){
    if(this.empty()){
      throw new Error("Queue is empty");
    }

    return this.Store[0];
  }

  back(){
    if(this.empty()){
      throw new Error("Queue is empty");
    }

    let len = this.Store.length, last = len - 1;
    return this.Store[last];
  }
}