Web/JavaScript/Reference/Global objects/Number/isSafeInteger

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

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`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