isFinite()
The isFinite()
function determines whether a value is finite, first converting the value to a number if necessary. A finite number is one that's not NaN
or ±Infinity
. Because coercion inside the isFinite()
function can be surprising, you may prefer to use Number.isFinite()
.
Try it
Syntax
isFinite(value)
Parameters
value
-
The value to be tested.
Return value
false
if the given value is NaN
, Infinity
, or -Infinity
after being converted to a number; otherwise, true
.
Description
isFinite()
is a function property of the global object.
When the argument to the isFinite()
function is not of type Number, the value is first coerced to a number, and the resulting value is then compared against NaN
and ±Infinity. This is as confusing as the behavior of isNaN
— for example, isFinite("1")
is true
.
Number.isFinite()
is a more reliable way to test whether a value is a finite number value, because it returns false
for any non-number input.
Examples
Using isFinite()
isFinite(Infinity); // false
isFinite(NaN); // false
isFinite(-Infinity); // false
isFinite(0); // true
isFinite(2e64); // true
isFinite(910); // true
// Would've been false with the more robust Number.isFinite():
isFinite(null); // true
isFinite("0"); // true
Specifications
Specification |
---|
ECMAScript Language Specification # sec-isfinite-number |
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