JavaScript队列或者堆栈的实现

Key Points :

array.splice(index, num);

// pop elements whose indices range from index to (index+num)from array.

then add element by push() method.

The rest concentration only needs to be focused on the end to be operated upon.

Tips :

Always keep in mind that the difference between stack and queue exists in the ends that are operated upon.

Stack : only one end is operated upon for both add and delete operation.

Queue : two ends are both operated upon, specifically to say, add in the start end and delete from the tail end.