如何在JavaScript中实现堆栈和队列？

var stack = [];
stack.push(2); // stack is now [2]
stack.push(5); // stack is now [2, 5]
var i = stack.pop(); // stack is now [2]
alert(i); // displays 5

var queue = [];queue.push(2);         // queue is now [2]queue.push(5);         // queue is now [2, 5]var i = queue.shift(); // queue is now [5]alert(i);   // displays 2