function Queue () {
collection = [];
this.print = function() {
console.log(collection);
};
this.enqueue = function(element) {
collection.push(element);
};
this.dequeue = function() {
return collection.shift();
};
this.front = function() {
return collection[0];
};
this.size = function() {
return collection.length;
};
this.isEmpty = function() {
return (collection.length === 0);
};
}