Parsing long number

Question

Can anybody explain why Number('31301006300002607') ( or parseInt('31301006300002607') ) returns 31301006300002610? Tried in Chrome and Firefox. Any implicit length restrictions?

Actually I need to validate up to 18-digits number along with truncating leading zeros but prefer to avoid regular expressions for such simple task.

If you also need to truncate then it's a string, not a number, and it's a trivial regex--how is that any less simple? — Dave Newton, Jan 08 '20 at 13:48
Does it matter that the output is imprecise? What are you actually trying validate here? — VLAZ, Jan 08 '20 at 13:49

score 3 · Answer 1 · answered Jan 08 '20 at 13:48

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The Number.MAX_SAFE_INTEGER constant represents the maximum safe integer in JavaScript (253 - 1).

For larger integers, consider using BigInt.

source https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER

answered Jan 08 '20 at 13:48

kooskoos

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Yep, `BigInt` should do the trick – assembler Jan 08 '20 at 13:52

score 0 · Answer 2 · answered Jan 08 '20 at 13:48

You can't represent an 18-digit number as a number. The maximum safe value is:

console.log(Number.MAX_SAFE_INTEGER);

which is 16-digit. Any value above that number is unsafe and can cause various issues with your code so you definitely should represent such big numbers as strings in your case.

Parsing long number

2 Answers2