Javascript中的栈、队列操作

   <script>
           let arr=[];
         //入栈push(),返回值为数组长度
            console.log(arr.push(1,2,3));
            console.log(arr);
            console.log(arr.push(4));
            console.log(arr);
            //出栈pop()
            console.log(arr.pop());
            console.log(arr);
            console.log(arr.pop());
            console.log(arr);
    </script>

   <script>
    arr=[];
        arr.unshift("a","b","c");
        console.log(arr);
        //入队列
        arr.unshift("d");
        console.log(arr);
        //出队列
        arr.shift();
        console.log(arr);
        arr.shift();
        console.log(arr);
   </script>