Added Queue Data Structure

Author: LumaLivy

Data Structures/Queue/Queue.js

@@ -0,0 +1,97 @@
+/* Queue
+* A Queue is a data structure that allows you to add an element to the end of
+* a list and remove the item at the front. A queue follows a "First In First Out"
+* system, where the first item to enter the queue is the first to be removed. This
+* implementation uses an array to store the queue.
+*/
+
+//Functions: enqueue, dequeue, peek, view, length
+
+var Queue = function() {
+
+  //This keeps track of where the end of the queue is
+  this.back = 0;
+  //This is the array representation of the queue
+  this.queue = {};
+
+  //Add a value to the end of the queue
+  this.enqueue = function(item) {
+    this.queue[this.back] = item;
+    this.back++;
+  }
+
+  //Removes the value at the front of the queue
+  this.dequeue = function() {
+    if (this.back === 0) {
+      return "Queue is Empty";
+    }
+
+    var result = this.queue[this.front];
+    delete this.queue[this.front];
+
+    //Shift all the other items forward
+    for (var i = 1; i < this.back; i++) {
+      this.queue[i - 1] = this.queue[i];
+    }
+
+    //clean up the leftover duplicated value at the back of the queue
+    delete this.queue[this.back];
+    this.back--;
+
+    return result;
+  }
+
+  //Return the length of the queue
+  this.length = function() {
+    return this.back;
+  }
+
+  //Return the item at the front of the queue
+  this.peek = function() {
+    return this.queue[0];
+  }
+
+  //List all the items in the queue
+  this.view = function() {
+    var str = "{"
+    //construct a single string to represent the items in the queue
+    for (var i = 0; i < this.back; i++) {
+      str += this.queue[i];
+      if (i !== this.back - 1) {
+        str += ", ";
+      }
+    }
+    str += "}";
+
+    console.log(str);
+  }
+}
+
+//Implementation
+var myQueue = new Queue();
+
+myQueue.enqueue(1);
+myQueue.enqueue(5);
+myQueue.enqueue(76);
+myQueue.enqueue(69);
+myQueue.enqueue(32);
+myQueue.enqueue(54);
+
+myQueue.view();
+
+console.log("Length: " + myQueue.length());
+console.log("Front item: " + myQueue.peek());
+console.log("Removed " + myQueue.dequeue() + " from front.");
+console.log("New front item: " + myQueue.peek());
+console.log("Removed " + myQueue.dequeue() + " from front.");
+console.log("New front item: " + myQueue.peek());
+myQueue.enqueue(55);
+console.log("Inserted 55");
+console.log("New front item: " + myQueue.peek());
+
+for (var i = 0; i < 5; i++) {
+  myQueue.dequeue();
+  myQueue.view();
+}
+
+console.log(myQueue.dequeue());