text: export default function Queue() {
    this.store = [];
  }
  
  Queue.prototype.enqueue = function(elem) {
    this.store.push(elem);
  }
  
  Queue.prototype.dequeue = function() {
    if (this.isEmpty()) {
      return null;
    }
    return this.store.shift();
  }
  
  Queue.prototype.isEmpty = function() {
    return this.store.length === 0;
  }