This question already has answers here:
JavaScript summing large integers
(10 answers)
Closed 6 months ago.
The output of the following:
let x = 10**23;
console.log(x.toString(16))
comes out 152d02c7e14af6000000 which actually computes to 99999999999999991611392 and not 10**23. Interestingly enough, the following doesn't compute to false:
let x = 10**23;
console.log(x==parseInt(x.toString(16),16))
Am I getting something wrong here?
JavaScript numbers are floating point, which lose precision the larger they get. When you exceed Number.MAX_SAFE_INTEGER (which is 253 – 1), the precision becomes >1.
This also means that things like 10**23 === (1**23 - 123) evaluates to true.
Related
This question already has answers here:
Large numbers erroneously rounded in JavaScript
(6 answers)
Closed 1 year ago.
I'm sure this has something to do with floating point math or something, but I need to out how to correctly interpret this number 9703248444284653. Javascript apparently doesn't like it
If I just do this.
var test = 9703248444284653
console.log(test)
The result is 9703248444284652, which is obviously not correct. Problem is that 9703248444284653 is an id that can't be changed. I have no idea what to do with this.
Your value is larger than Number.MAX_SAFE_INTEGER.
console.log(9703248444284653n > Number.MAX_SAFE_INTEGER);
You should treat your IDs as BigInt values. So you can should probably store the values as strings and then parse them as BigInt values if you need to perform any math on them.
const
bigIntNative = 9703248444284653n,
bigIntConstructed = BigInt('9703248444284653');
console.log(typeof bigIntNative === 'bigint' && bigIntNative === bigIntConstructed);
console.log(`${bigIntNative}`);
This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 3 years ago.
console.log(Number.MIN_VALUE); // 5e-324
console.log(Number.MIN_VALUE - 1); // -1
Value of Number.MIN_VALUE is 5e-324, but if I subtract 1 from it, -1 is returned.
It looks like some garbage value but I'm wondering why JavaScript interpreter cannot represent it. Otherwise, Number.MAX_VALUE + 1 is same with Number.MAX_VALUE(1.7976931348623157e+308).
Is there something different between calculating Numbers.MAX_VALUE and Numbers.MIN_VALUE?
Number.MIN_VALUE - 1 is equal to -0.99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
I think any reasonable person would consider that to be -1, even before accounting for things like floating point inaccuracy :)
To be clear, Number.MIN_VALUE is the smallest value greater than zero that can be represented. It is not "negative Number.MAX_VALUE" as you appear to expect.
This question already has an answer here:
What is the standard solution in JavaScript for handling big numbers (BigNum)?
(1 answer)
Closed 6 years ago.
n = "11004691915666669"
parseInt(n)
parseInt(n, 10)
Both results are: 11004691915666668
This is off by one. I tested some other values and they convert correctly. Is this a bug in the library or is there a better way to convert?
See this SO question for more details. Your value is beyond the maximum integer that Javascript can represent with full accuracy.
Under the hood Javascript doesn't understand integers, everything's floating point. You're hitting the reduced accuracy that happens when you get to very large numbers.
From the Javascript reference at MDN given here.
The integer range for a Number is defined as follows :
var biggestInt = 9007199254740992;
var smallestInt = -9007199254740992;
Which is why since your number exceeds the biggestInt value preset by Javascript, the parseInt method only returns the integer value that lies within the Integer range for a Number in Javascript as defined above.
This question already has answers here:
Large numbers erroneously rounded in JavaScript
(6 answers)
Javascript parseInt() with leading zeros
(7 answers)
Closed 7 years ago.
I'm trying to convert a string to number in Javascript, but here is my problem :
var string = "068999999501111443";
parseInt(string); // 68999999501111440
Number(string); // 68999999501111440
Why does this happen and how to fix it ?
Thanks
This is because the number is too large to be stored accurately. It is being stored as a floating point number, which can only store a certain amount of precision. Beyond it's maximum precision, you'll get what look like weird rounding errors.
You'll get similar effects for decimals with a large number of decimal places. This is more well known, as it tends to occur more often, but it's exactly the same effect that is happening here.
This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 8 years ago.
This code snippet:
Math.pow(10,20)+20000 == Math.pow(10,20) + 10000
evaluates to true. Is this a JS bug?
No. Javascript uses floating point numbers to represent large values, and the value 1020 exceeds the precision of the floating point numbers. When you add a relatively tiny value such as 20000 or 10000 to the result, the resulting sums are indistinguishable.