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.

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.

Examples

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

Polyfill

Number.isSafeInteger = Number.isSafeInteger || function (value) {
   return Number.isInteger(value) && Math.abs(value) <= Number.MAX_SAFE_INTEGER;
};

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Number.isSafeInteger' in that specification.	Standard	Initial definition.
ECMAScript 2017 Draft (ECMA-262) The definition of 'Number.isSafeInteger' in that specification.	Draft

Browser compatibility

See also

• The Number object it belongs to.
• Number.MIN_SAFE_INTEGER
• Number.MAX_SAFE_INTEGER