Stack & Queue • Operations

Dequeue Operation

Dequeue is the process of removing an element from a Queue. In a FIFO structure, removals always happen at the 'Front'.

Underflow Check

Before dequeuing, we must check if the queue is empty (`front == -1` or `front > rear`). Dequeuing from an empty queue causes an Underflow error.

The Front Pointer

We read the value at the `front` index, and then increment `front` by 1. The element isn't necessarily deleted from memory immediately, but it is ignored by the queue logic.

Resetting

If `front` overtakes `rear` after a dequeue, it means the queue has become completely empty. We reset both pointers to `-1`.

FRONT

10

[0]

20

[1]

30

REAR

[2]

[3]

[4]

Code Tracker

:::

1function dequeue() {

2 if (front === -1 || front > rear) {

3 console.log('Queue Underflow');

4 return;

5 }

6 let val = queue[front];

7 front++;

8 if (front > rear) { // Reset if empty

9 front = -1; rear = -1;

10 }

11 return val;

12}