Wrong value when parsing a number of type String to Number

Question

I have the following string:

var x = "10207122232230383";

When parsing it to integer i get the same number + 1.

var y = parseInt(x, 10);
console.log(y);

This prints 10207122232230384. Why is this happening?

`Number.MAX_SAFE_INTEGER` is the max value that you can represent with javascript without "loosing precision". this number is over that limit. see [this post](http://stackoverflow.com/questions/307179/what-is-javascripts-highest-integer-value-that-a-number-can-go-to-without-losin) — Hacketo, Nov 12 '15 at 10:43
From the code above it looks as though you are passing an int and not the original string? — OliverRadini, Nov 12 '15 at 10:43
@VanderVidi if you don't do math on this number, keep it as string, else could use some biginteger library I guess. — Hacketo, Nov 12 '15 at 10:47
http://stackoverflow.com/questions/5353388/javascript-parsing-int64 — sayingu, Nov 12 '15 at 11:00

score 3 · Answer 1 · edited May 23 '17 at 12:15

3

The number is too large for js to parse as an integer. This is explained well in this post:

What is JavaScript's highest integer value that a Number can go to without losing precision?

From a practical point of view, you can handle large numbers in javascript using a library, for instance https://github.com/MikeMcl/bignumber.js/

There are other libraries available which will help you to achieve the same thing, they are discussed at length here: https://github.com/MikeMcl/big.js/issues/45

edited May 23 '17 at 12:15

Community

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answered Nov 12 '15 at 10:47

OliverRadini

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Care to explain the downvote? Would appreciate it. – OliverRadini Nov 12 '15 at 10:48
Dunno but maybe try to explain the problem and someone will give you an upvote as a compensation. – Tomáš Zato Nov 12 '15 at 10:51
How about now? Doesn't make sense to me to go into a whole load of detail when the question has been answered well elsewhere. – OliverRadini Nov 12 '15 at 10:57
My bad - updated the answer now. – OliverRadini Nov 12 '15 at 11:08

score 2 · Accepted Answer · answered Nov 12 '15 at 11:12

In Javascript any integer which until unless cross Number.MAX_SAFE_INTEGER

that will be precision free.When it crosses this MAX_SAFE_INTEGER then it starts representing the doubleprecision 64-bit format IEEE 754 values as specified in the IEEE Standard for Binary Floating-Point Arithmetic.

To Over Come this You can go with any one of this libraries BigNum or Biginteger.

score 1 · Answer 3 · answered Nov 12 '15 at 10:59

That number is too large to be represented as an integer. You will have to use a BigNumber library as Javascript does not have a long type. You could, for example, use the the BigInt library developed by Michael M, below I have given an example how to use it.

document.write('Maximum value integer in JavaScript: ' + Number.MAX_SAFE_INTEGER + '<br>')
x = new BigNumber("10207122232230383")
document.write('Your value divided by 1: ' + x.div(1) + '<br>')
document.write('Your value divided by 3: ' + x.div(3) + '<br>')

<script src="https://cdnjs.cloudflare.com/ajax/libs/bignumber.js/2.1.0/bignumber.js"></script>

Wrong value when parsing a number of type String to Number

3 Answers3