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NaN and Infinity example in JavaScript
In JavaScript, NaN (Not-a-Number) and Infinity are special numeric values that represent invalid or infinite calculations. Understanding these values is crucial for handling mathematical operations and validation.
What is NaN?
NaN represents a value that is "Not-a-Number". It occurs when a mathematical operation fails or produces an undefined result.
<!DOCTYPE html>
<html>
<head>
<title>NaN Examples</title>
</head>
<body>
<script>
let results = document.getElementById('nanResults');
// Common ways NaN is produced
results.innerHTML = 'Number("Hello") = ' + Number("Hello") + '<br>';
results.innerHTML += 'Math.sqrt(-1) = ' + Math.sqrt(-1) + '<br>';
results.innerHTML += '0 / 0 = ' + (0 / 0) + '<br>';
results.innerHTML += 'parseInt("abc") = ' + parseInt("abc");
</script>
</body>
</html>
Number("Hello") = NaN
Math.sqrt(-1) = NaN
0 / 0 = NaN
parseInt("abc") = NaN
What is Infinity?
Infinity represents a number greater than any other number. It can be positive or negative.
<!DOCTYPE html>
<html>
<head>
<title>Infinity Examples</title>
</head>
<body>
<script>
let results = document.getElementById('infinityResults');
// Ways to get Infinity
results.innerHTML = '1 / 0 = ' + (1 / 0) + '<br>';
results.innerHTML += '-1 / 0 = ' + (-1 / 0) + '<br>';
results.innerHTML += 'Number.POSITIVE_INFINITY = ' + Number.POSITIVE_INFINITY + '<br>';
results.innerHTML += 'Number.NEGATIVE_INFINITY = ' + Number.NEGATIVE_INFINITY;
</script>
</body>
</html>
1 / 0 = Infinity -1 / 0 = -Infinity Number.POSITIVE_INFINITY = Infinity Number.NEGATIVE_INFINITY = -Infinity
Checking for NaN and Infinity
JavaScript provides built-in functions to detect these special values:
<!DOCTYPE html>
<html>
<head>
<title>Testing NaN and Infinity</title>
</head>
<body>
<script>
let results = document.getElementById('testResults');
let nanValue = Number("invalid");
let infValue = 1 / 0;
results.innerHTML = 'isNaN(' + nanValue + ') = ' + isNaN(nanValue) + '<br>';
results.innerHTML += 'Number.isNaN(' + nanValue + ') = ' + Number.isNaN(nanValue) + '<br>';
results.innerHTML += 'isFinite(' + infValue + ') = ' + isFinite(infValue) + '<br>';
results.innerHTML += 'Number.isFinite(' + infValue + ') = ' + Number.isFinite(infValue);
</script>
</body>
</html>
isNaN(NaN) = true Number.isNaN(NaN) = true isFinite(Infinity) = false Number.isFinite(Infinity) = false
Key Differences
| Value | When It Occurs | Detection Method |
|---|---|---|
NaN |
Invalid mathematical operations | Number.isNaN() |
Infinity |
Division by zero (non-zero numerator) | !Number.isFinite() |
-Infinity |
Negative division by zero | !Number.isFinite() |
Conclusion
NaN occurs from invalid operations while Infinity results from division by zero. Use Number.isNaN() and Number.isFinite() to properly detect these special values in your applications.
Updated on: 2026-03-15T23:18:59+05:30
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