js:数据结构笔记4--队列

function Queue() {
   this.dataStore = [];
   this.enqueue = enqueue;
   this.dequeue = dequeue;
   this.front = front;
   this.back = back;
   this.length = length;
   this.toString = toString;
   this.isEmpty = isEmpty;
}
function enqueue(elem) {
   this.dataStore.push(elem);
}
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 length() {
   return this.dataStore.length;
}
function isEmpty() {
   if(this.dataStore.length === 0) {
      return true;
   } else {
      return false;
   }
}