Number.isInteger()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The Number.isInteger()
static method determines whether the passed value is an integer.
Try it
Syntax
Number.isInteger(value)
Parameters
value
-
The value to be tested for being an integer.
Return value
The boolean value true
if the given value is an integer. Otherwise false
.
Description
If the target value is an integer, return true
, otherwise return false
. If the value is NaN
or Infinity
, return false
. The method will also return true
for floating point numbers that can be represented as integer. It will always return false
if the value is not a number.
Note that some number literals, while looking like non-integers, actually represent integers — due to the precision limit of ECMAScript floating-point number encoding (IEEE-754). For example, 5.0000000000000001
only differs from 5
by 1e-16
, which is too small to be represented. (For reference, Number.EPSILON
stores the distance between 1 and the next representable floating-point number greater than 1, and that is about 2.22e-16
.) Therefore, 5.0000000000000001
will be represented with the same encoding as 5
, thus making Number.isInteger(5.0000000000000001)
return true
.
In a similar sense, numbers around the magnitude of Number.MAX_SAFE_INTEGER
will suffer from loss of precision and make Number.isInteger
return true
even when it's not an integer. (The actual threshold varies based on how many bits are needed to represent the decimal — for example, Number.isInteger(4500000000000000.1)
is true
, but Number.isInteger(4500000000000000.5)
is false
.)
Examples
Using isInteger
Number.isInteger(0); // true
Number.isInteger(1); // true
Number.isInteger(-100000); // true
Number.isInteger(99999999999999999999999); // true
Number.isInteger(0.1); // false
Number.isInteger(Math.PI); // false
Number.isInteger(NaN); // false
Number.isInteger(Infinity); // false
Number.isInteger(-Infinity); // false
Number.isInteger("10"); // false
Number.isInteger(true); // false
Number.isInteger(false); // false
Number.isInteger([1]); // false
Number.isInteger(5.0); // true
Number.isInteger(5.000000000000001); // false
Number.isInteger(5.0000000000000001); // true, because of loss of precision
Number.isInteger(4500000000000000.1); // true, because of loss of precision
Specifications
Specification |
---|
ECMAScript Language Specification # sec-number.isinteger |
Browser compatibility
BCD tables only load in the browser