How to round off 9999999999999999 to 9999999999999998

Question

In my case, i am converting a string value of '9999999999999999' to integer using parseFloat(). But it converts to next number of it i.e. 10000000000000000. But i need to convert it to before of that number i.e. 999999999999999998. I have searched for a while in google. But could not get clear idea to implement this.

"converting ... to integer using parseFloat" :) ... more seriously - unlikely as this number does not fit to int. — Alexei Levenkov, May 17 '13 at 06:31

score 0 · Answer 1 · answered May 17 '13 at 06:30

0

Try this

document.getElementById("demo").innerHTML=Math.round(9999999999999999-2);

OUTPUT

9999999999999998

answered May 17 '13 at 06:30

Nidhish Krishnan

20,593
6
63
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:) and `(9-2)` should be rounded to `8` obviously. – Alexei Levenkov May 17 '13 at 06:33

score 0 · Answer 2 · answered May 17 '13 at 06:37

This number is too big to represented precisely in JavaScript Number value. So no amount of conversion will give you values reliably/precisly as you want around such range.

I.e. (9999999999999999-1)===(9999999999999999) returns true, but (9999999999999998)===(9999999999999999) returns false.

If you need such high precision in JavaScript (similar to many other languages) you need to use specialized data types (unfortunately there is no "BigInteger" type built in in JavaScript).

score 0 · Answer 3 · edited May 23 '17 at 11:57

You will need to use some external javascript library to work with big numbers like that, cause max number you cant represent without losing presicion in javascript integers is 9007199254740992 (Explanation : What is JavaScript's highest integer value that a Number can go to without losing precision?)

Here you have some link where people discuss about some libraries to use for javascript big numbers. How to deal with big numbers in javascript

How to round off 9999999999999999 to 9999999999999998

3 Answers3