JavaScript .isSafeInteger()

The .isSafeInteger() method is a static method of the Number object in JavaScript which determines whether the provided value is a safe integer: an integer that can be exactly represented using the IEEE-754 double-precision format.

A safe integer satisfies:

$$ -(2^{53} - 1) \leq \text{value} \leq 2^{53} - 1 $$

If the condition holds, the method returns true, otherwise, it returns false.

Syntax

Number.isSafeInteger(value);

Parameters:

• value: The value to be tested for being a safe integer.

Return value:

Returns true if the given value is of type number, is an integer, and is within the safe integer range (-(2^53 - 1) to 2^53 - 1). Otherwise, it returns false.

Example

This example demonstrates how .isSafeInteger() returns true for integers and false for non-integers or values outside the safe range:

console.log(Number.isSafeInteger(10));
console.log(Number.isSafeInteger(3.14));
console.log(Number.isSafeInteger(Math.pow(2, 53)));
console.log(Number.isSafeInteger(2 ** 53 - 1));

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The output of this code is:

true
false
false
true

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Codebyte Example

This codebyte tests various values to show how the method handles whole numbers, decimals, and edge cases at the limits of JavaScript’s safe integer range:

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