两个栈实现一个队列

let stack1 = [], stack2 = []
function push(node)
{
    // write code here
    stack1.push(node);
}
function pop()
{
    // write code here
    if(!stack2.length){
        while(stack1.length){
            stack2.push(stack1.pop())
        }
    }
    return stack2.pop()
}
module.exports = {
    push : push,
    pop : pop
};