Possible Javascript numerical bug [duplicate] - javascript

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.

Related

Why 888888888888888888888 equals 888888888888888900000 in JavaScript [duplicate]

This question already has answers here:
Why are two different numbers equal in JavaScript?
(4 answers)
How to deal with floating point number precision in JavaScript?
(47 answers)
Is floating point math broken?
(31 answers)
Closed 3 years ago.
Why 888888888888888888888 equals 888888888888888900000 in JavaScript
console.log(888888888888888888888 === 888888888888888900000)
in chrome console
That is because integers can only be precisely represented in JavaScript up to 2^53 - 1
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
The problem is that, after 2^53 - 1, there is not enough bits to represent the number. So, when you set a higher number, you lose information and what you are actually storing in memory is not reliable. In your case, these 2 numbers, after converting to binary, are the same. That is why they are equal

How to add fraction and whole number number in javascript? [duplicate]

This question already has answers here:
How to deal with floating point number precision in JavaScript?
(47 answers)
Closed 5 years ago.
for example in javascript addition of 1 + 0.59 is 1.5899999999999999 but I want output of 1.59 which looks right to me.
Use .toFixed() to round your number.
alert((1+0.58999999999).toFixed(2));

Is it possible to correctly do math on numbers greater than 2^53? [duplicate]

This question already has answers here:
Large integers in javascript (more the 2^53-1)
(2 answers)
What is JavaScript's highest integer value that a number can go to without losing precision?
(21 answers)
Closed 7 years ago.
I am making a calculator in JavaScript that needs to be able to do precise math on numbers larger than 2^53, which is 9007199254740992. Is there any way to do this?
You can use the "strint" library https://github.com/rauschma/strint.
For example:
> var strint = require("./strint");
> strint.add("9007199254740992", "1")
'9007199254740993'

String to number is wrong [duplicate]

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.

javascript math result lesser than 0 gets 0.0000000000 [duplicate]

This question already has answers here:
Is floating point math broken?
(31 answers)
Closed 7 years ago.
Why does javascript returns so many zeros and not just 0.24
And how can i disable javascript to do this. Because when im using a calculator i never get the result 0.24000000000002
var sum = (0.0001 * 2400);
result 0.2400000000002
The reason for this is that your sum is a float which are known to not be very precise. This is a limitation of float values.
To fix this you need to round the decimals by either Math.round or .toFixed.
javascript always do that but you can make it show only 2 digits after the dot.
var sum = (0.0001 * 2400);
alert(sum.toFixed(2));

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