js:数据结构笔记3--栈

function Stack() {
   this.dataStore = [];
   this.top = 0;
   this.push = push;
   this.pop = pop;
   this.peek = peek; 
   this.length = length;
   this.clear =clear; 
}
function push(elem) {
   this.dataStore[this.top++] = elem;
}
function pop() {
	var data = this.dataStore[--this.top];
	this.dataStore.length = this.top;
   return data;
}
function peek() {
   return this.dataStore[this.top--];
}
function length() {
   return this.top;
}
function clear() {
   this.top = 0;
}