November 21, 2021

How to Detect Arrow Keys in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to detect arrow keys in javascript. In a standard keyboard layout, we have 4 arrows left, right, up, and down. The arrow keys are located right before the numpad on the keyboard. They are generally used to change cursor position in a textbox as well as help in scrolling a webpage.

Whenever we press an arrow key or any other key on the keyboard, certain keyboard events are triggered. In the event handler function, the event object contains details about the keyboard event. The event object has a key property that can reveal which key has been pressed by the user.

To keep things simple, we are going to monitor keydown event and in the event handler function, we will verify whether an arrow key is pressed or not.

In the following example, we have an input field. As soon as the user presses an arrow key while typing in the input field, we will display a message on the screen. Please have a look over the code example and the steps given below.

HTML & CSS

We have 3 elements in the HTML file (div, h1, and textarea).
The div element is just a wrapper for the rest of the elements. We are using style attribute with div element to center align the child elements.
The innerText for the h1 element is “Result”.
We have also included our javascript file script.js with a script tag at the bottom.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
      
    <div style="text-align: center">
        <textarea cols="50" rows="5" placeholder="Enter Text"></textarea>
        <h1>Result</h1>
    </div>
    <script src="script.js"></script>
</body>
</html>

Javascript

We have selected the textarea element and h1 element using document.querySelector() method and stored them in the input and result variables respectively.
We have attached keydown event listener to the textarea element.
In the event handler function, we are using switch statement and key property of the event object to verify which arrow key is pressed or not.
Depending upon the result of verification, we are updating innerText of the h1 element.

let input = document.querySelector("textarea");
let result = document.querySelector("h1");

input.addEventListener("keydown", (e) => {
  switch (e.key) {
    case "ArrowLeft":
      result.innerText = "Left Arrow";
      break;
    case "ArrowRight":
      result.innerText = "Right Arrow";
      break;
    case "ArrowUp":
      result.innerText = "Up Arrow";
      break;
    case "ArrowDown":
      result.innerText = "Down Arrow";
      break;
  }
});

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