CODEWITHSUNDEEP
javascript
jcalfee314
jcalfee314

Reputation: 4830

Detecting a number overflow in JavaScript at the time of base10 string conversion

The code evaluates true when the number string is within +/- 2^53 and false when it is outside of that range.

num_string = "9007199254740992"
new_num = (new Number(num_string)+"")
num_string === new_num

This seems to work, but what is the correct way to detect a number overflow? This would fail, for example, if the initial string had leading zeros 007. This is not an overflow, that should not fail.

EDIT: I have to use a string, I'm converting to from a string to a number and want to know if my number got messed up. So, I am testing a string (not a number).

Upvotes: 2

Views: 57

Answers (1)

Jivings
Jivings

Reputation: 23250

You don't need to use a string:

9007199254740993 === 9007199254740992 // true

However, you should be checking against Number.MAX_SAFE_INTEGER, which will tell you the highest integer you can use without loss of precision.

Number.MAX_SAFE_INTEGER // 9007199254740991

So check against that:

if (num > Number.MAX_SAFE_INTEGER) {
  // not safe!
}

You can also use a function (credit to @RickHitchcock):

Number.isSafeInteger(num)

Upvotes: 2

Related Questions