From this [Queue](https://github.com/TheAlgorithms/Javascript/blob/ad68c639476804a27342e3416d060cec1f5037ba/Data-Structures/Queue/Queue.js#L28) implementation I believe the Operation is **O(n)** cause the complexity of `Array.prototype.shift` methods is **O(n)**, [see](https://stackoverflow.com/questions/22614237/javascript-runtime-complexity-of-array-functions)
