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JavaScript Number method: isFinite()

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The isFinite() method (of the JavaScript Number object) returns true if value is a finite number, otherwise returns false.

 

It has the following syntax with the following parameters:

 

Number.isFinite(x)

 

Parameter

Required / Optional

Description

x

Required

Input parameter

 

The Number.isFinite method is subtly different to the global isFinite function. The latter coerces a value to a number before testing it, whilst the former does not. So, Number.isFinite("4.3") returns false, whilst isFinite("4.3") returns true.

 

EXAMPLE:


HTML USED IN THIS EXAMPLE:
<!DOCTYPE html>
<html> <!-- Copyright (c) Nematrian Limited 2018 -->
<head>
<style>
table,th,tr,td {border: 1px solid black; border-collapse :collapse;}
</style>
</head>
<body>
<table>
<tr>
<th>Example</th>
<th>Resulting value of <code>x</code></th>
</tr>
<tr>
<td><code id="Example"></code></td>
<td><code id="Result"></code></td>
</tr>
</table>

<script>
document.getElementById("Example").innerHTML =
  'var x = Number.isFinite(Number.MAX_VALUE * 2);';
document.getElementById("Result").innerHTML =
  Number.isFinite(Number.MAX_VALUE * 2);
</script>

</body>
</html>

FUNCTION THAT MAY ASSIST IN TESTING WHETHER FEATURE IS SUPPORTED:
function isSupportedJavaScriptMethodNumberIsFinite() {
  var z = 12.5; return !!z.isFinite;
}


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