Learning JavaScript? Download my free JavaScript Handbook 🔥

A number might satisfy Number.isInteger() but not Number.isSafeInteger() if it goes out of the boundaries of safe integers, which I explained above.

So, anything over 2^53 and below -2^53 is not safe:

Number.isSafeInteger(Math.pow(2, 53)) // false
Number.isSafeInteger(Math.pow(2, 53) - 1) // true
Number.isSafeInteger(Math.pow(2, 53) + 1) // false
Number.isSafeInteger(-Math.pow(2, 53)) // false
Number.isSafeInteger(-Math.pow(2, 53) - 1) // false
Number.isSafeInteger(-Math.pow(2, 53) + 1) // true

Edit this page

Here's my latest YouTube video. I talk about why I think that dogs are a great help for developers working remotely: