1 function Stack() { 2   this.dataStore = []; 3   this.top = 0; //指向栈顶的位置 4   this.push = push; 5   this.pop = pop; 6   this.peek = peek; 7   this.clear = clear; 8   this.length = length; 9   10   function push(element) {11     this.dataStore[this.top++] = element; //先赋值后++12   }13   14   function peek() {15     return this.dataStore[this.top - 1];16   }17 18   function pop() {19     return this.dataStore[--this.top]; //先--运算20   }21 22   function clear() {23     this.top = 0;24   }25 26   function length() {27     return this.top;28   }29 }30 31 var s = new Stack(); 32 s.push("David"); 33 s.push("Raymond"); 34 s.push("Bryan"); 35 console.log(s);36 console.log("length: " + s.length());

 

 

注意：

这样的一步操作arr[i++]="ddd";----》这里的执行顺序是：先执行赋值后进行的++运算

等价于下面的两布操作：

arr[i] = "ddd";

i++;

 

 

//这样写才是先执行++运算

arr[++i]="ddd";