The Number.isSafeInteger()
method determines whether the provided value is a number that is a safe integer.
A safe integer is an integer that
- can be exactly represented as an IEEE-754 double precision number, and
- whose IEEE-754 representation cannot be the result of rounding any other integer to fit the IEEE-754 representation.
For example, 253 - 1
is a safe integer: it can be exactly represented, and no other integer rounds to it under any IEEE-754 rounding mode. In contrast, 253
is not a safe integer: it can be exactly represented in IEEE-754, but the integer 253 + 1
can't be directly represented in IEEE-754 but instead rounds to 253
under round-to-nearest and round-to-zero rounding. The safe integers consist of all integers from -(253 - 1)
inclusive to 253 - 1
inclusive (± 9007199254740991
or ± 9,007,199,254,740,991).
Handling values larger or smaller than ~9 quadrillion with full precision requires using an arbitrary precision arithmetic library. See What Every Programmer Needs to Know about Floating Point Arithmetic for more information on floating point representations of numbers.
For larger integers, consider using the BigInt
type.
Syntax
Number.isSafeInteger(testValue)
Parameters
testValue
- The value to be tested for being a safe integer.
Return value
A Boolean
indicating whether or not the given value is a number that is a safe integer.
Polyfill
Number.isSafeInteger = Number.isSafeInteger || function (value) { return Number.isInteger(value) && Math.abs(value) <= Number.MAX_SAFE_INTEGER; };
Examples
Using isSafeInteger
Number.isSafeInteger(3); // true Number.isSafeInteger(Math.pow(2, 53)); // false Number.isSafeInteger(Math.pow(2, 53) - 1); // true Number.isSafeInteger(NaN); // false Number.isSafeInteger(Infinity); // false Number.isSafeInteger('3'); // false Number.isSafeInteger(3.1); // false Number.isSafeInteger(3.0); // true
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Number.isSafeInteger' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
isSafeInteger | Chrome Full support 34 | Edge Full support 12 | Firefox Full support 32 | IE No support No | Opera Full support 21 | Safari Full support 10 | WebView Android Full support ≤37 | Chrome Android Full support 34 | Firefox Android Full support 32 | Opera Android Full support 21 | Safari iOS Full support 10 | Samsung Internet Android Full support 2.0 | nodejs Full support 0.12 |
Legend
- Full support
- Full support
- No support
- No support
See also
- The
Number
object it belongs to. Number.MIN_SAFE_INTEGER
Number.MAX_SAFE_INTEGER
BigInt