FIFO behavior for Array.pop in javascript?

The method is array.shift(). It pulls the first array element much as array.pop() pulls the last element.

You can use array.prototype.shift()

>> array = [];
>> array.push(1);
>> array.push(2);
>> array.push(3);
>> array.shift();  //outputs 1 and removes it from the array

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/shift