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JavaScript - detect when left arrow key was pressed

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Created by:

Brandy-Mccabe

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In this article, we would like to show you how to detect when the left arrow key was pressed using JavaScript.

In the below solutions, we use some legacy functions that lets to get key code. The main reason why that approach was used, is the time when event.key and key.code were introduced in the major web browsers (around 2016-2017).

Practical examples

Edit

Both of the examples below provide the legacy support for the keyCode property which represents an integer value (37) of the left arrow key instead of a string (ArrowLeft).

Example 1

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In this example, we use event.key to get the value of the key pressed by the user and then check if it's a left arrow.

xxxxxxxxxx
 
<!doctype html>
<html>
<body>
  <div>Click here to get focus and press left arrow key.</div>
  <script>
​
    var MAPPING = {
        37: 'ArrowLeft',
    };
​
     function getKey(event) {
        return event.key || MAPPING[event.keyCode]; // with legacy support
    }
​
     document.addEventListener('keydown', function(event) {
        var key = getKey(event);
        if (key === 'ArrowLeft') {
            console.log('Arrow left pressed.');
        }
    });
​
  </script>
</body>
</html>

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Example 2

Edit

In this example, we use event.code to get the value of the key pressed by the user and then check if it's a left arrow.

xxxxxxxxxx
 
<!doctype html>
<html>
<body>
  <div>Click here to get focus and press left arrow key.</div>
  <script>
​
    var MAPPING = {
        37: 'ArrowLeft',
    };
​
    function getCode(event) {
        return event.code || MAPPING[event.keyCode]; // with legacy support
    }
​
    document.addEventListener('keydown', function(event) {
        var code = getCode(event);
        if (code === 'ArrowLeft') {
            console.log('Arrow left pressed.');
        }
    });
​
  </script>
</body>
</html>