JavaScript const

JavaScript const keyword is used to declare a constant value. A constant has to be declared and immediately initialized. Meaning, declaration and initialization of a constant has to happen in a single statement.

A constant once initialised, cannot be modified.

The syntax to define a constant pi with value 3.14 is

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const pi = 3.14;

Example

In the following example, we create a constant pi with value 3.14 and use it as inner HTML for a pre HTML element.

index.html

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<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        const pi = 3.14;
        document.getElementById('output').innerHTML += pi;
    </script>
</body>
</html>

Conclusion

In this JavaScript Tutorial, we learned what constants are, how to declare/initialize them, and how to use them in a program, with examples.

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JavaScript const