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isFinite() function in JavaScript
The isFinite() function accepts a value and determines whether the given value is a finite number or not. If so, this method returns true, else it returns false. You can also invoke this method using the Number object as Number.isFinite().
Syntax
isFinite(value) Number.isFinite(value)
Parameters
value: The value to be tested for finiteness.
Return Value
Returns true if the value is a finite number, false otherwise.
Example: Basic Usage
<html>
<head>
<title>JavaScript Example</title>
</head>
<body>
<script type="text/javascript">
var result1 = Math.min();
document.write(isFinite(result1));
document.write("<br>");
var result2 = Number.isFinite(100/0);
document.write(result2);
document.write("<br>");
var result3 = Math.max(25, 36, 862);
document.write(isFinite(result3));
</script>
</body>
</html>
false false true
Example: Testing Different Values
<html>
<head>
<title>isFinite Examples</title>
</head>
<body>
<script type="text/javascript">
// Finite numbers
document.write("isFinite(42): " + isFinite(42) + "<br>");
document.write("isFinite(-10.5): " + isFinite(-10.5) + "<br>");
// Infinite values
document.write("isFinite(Infinity): " + isFinite(Infinity) + "<br>");
document.write("isFinite(-Infinity): " + isFinite(-Infinity) + "<br>");
// NaN and strings
document.write("isFinite(NaN): " + isFinite(NaN) + "<br>");
document.write("isFinite('123'): " + isFinite('123') + "<br>");
document.write("isFinite('hello'): " + isFinite('hello') + "<br>");
</script>
</body>
</html>
isFinite(42): true
isFinite(-10.5): true
isFinite(Infinity): false
isFinite(-Infinity): false
isFinite(NaN): false
isFinite('123'): true
isFinite('hello'): false
Difference Between isFinite() and Number.isFinite()
<html>
<head>
<title>isFinite vs Number.isFinite</title>
</head>
<body>
<script type="text/javascript">
// Global isFinite() converts to number first
document.write("isFinite('42'): " + isFinite('42') + "<br>");
document.write("Number.isFinite('42'): " + Number.isFinite('42') + "<br>");
document.write("isFinite(null): " + isFinite(null) + "<br>");
document.write("Number.isFinite(null): " + Number.isFinite(null) + "<br>");
</script>
</body>
</html>
isFinite('42'): true
Number.isFinite('42'): false
isFinite(null): true
Number.isFinite(null): false
Comparison
| Method | Type Conversion | String '42' | null |
|---|---|---|---|
isFinite() |
Yes | true | true |
Number.isFinite() |
No | false | false |
Conclusion
Use isFinite() to check if a value is a finite number. For stricter type checking without conversion, use Number.isFinite() which only returns true for actual numbers.
Updated on: 2026-03-15T23:18:59+05:30
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