javascript queue class

function Queue() {
   this.dataStore = [];
   this.enqueue = enqueue;
   this.dequeue = dequeue;
   this.front = front;
   this.back = back;
   this.toString = toString;
   this.empty = empty;
}

function enqueue(element) {
   this.dataStore.push(element);
}

function dequeue() {
   return this.dataStore.shift();
}

function front() {
   return this.dataStore[0];
}

function back() {
   return this.dataStore[this.dataStore.length-1];
}

function toString() {
   var retStr = "";
   for (var i = 0; i < this.dataStore.length; ++i) {
      retStr += this.dataStore[i] + "\n";
   }
   return retStr;
}

function empty() {
   if (this.dataStore.length == 0) {
      return true;
   }
   else {
      return false;
   }
}