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How to Check if a Variable is a Number in Javascript?

JavaScript ·

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In this tutorial, you will learn check whether variable is number or string in javascript. you can see how to check if a variable is a number in javascript. I would like to share with you check whether variable is number or string in javascript. I explained simply step by step 3 ways to check if variable is a number in javascript. you will do the following things for how to check whether a var is string or number using javascript.

There are several ways to check if a variable is a number in JavaScript:

Example 1: Using the typeof operator


<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>How to Check if a Variable is a Number in Javascript? - NiceSnippets.Com</title>
</head>
<body>
</body>
<script type="text/javascript">
    let num = 123;
    if (typeof num === 'number') {
      console.log('num is a number');
    }
</script>
</html>

Example 2: Using the isNaN() function 

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>How to Check if a Variable is a Number in Javascript? - NiceSnippets.Com</title>
</head>
<body>
</body>
<script type="text/javascript">
    let num = 'abc';
    if (!isNaN(num)) {
      console.log('num is a number');
    }
</script>
</html>

Example 3: Using regular expressions 

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>How to Check if a Variable is a Number in Javascript? - NiceSnippets.Com</title>
</head>
<body>
</body>
<script type="text/javascript">
    let num = '123';
    if (/^\d+$/.test(num)) {
      console.log('num is a number');
    }
</script>
</html>

Example 4: Using the Number() function 

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>How to Check if a Variable is a Number in Javascript? - NiceSnippets.Com</title>
</head>
<body>
</body>
<script type="text/javascript">
    let num = '123';
    if (!isNaN(Number(num))) {
      console.log('num is a number');
    }
</script>
</html>

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