isFinite() - JavaScript | MDN
Try it
function div(x) {
if (isFinite(1000 / x)) {
return "Number is NOT Infinity.";
}
return "Number is Infinity!";
}
console.log(div(0));
// Expected output: "Number is Infinity!""
console.log(div(1));
// Expected output: "Number is NOT Infinity."
Syntax
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()
js
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® 2027 Language Specification # sec-isfinite-number |