Comparing large numbers with javascript [duplicate] - javascript

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Subtracting long numbers in javascript
Can anyone tell me how to compare large numbers in javascript?
Something like
var sla = 1263293940000;
var resp = 1263296389700;
if(sla > resp)
{
//do something
}

You might want to look into the BigInteger library.

Internally all javascript numbers are represented as double-precision floating point numbers. As you've discovered, this causes some rounding errors for very large numbers (and in other places). If you need more precision, you'll need to use a library like the one Alex posted.

return new Number(first)>new Number(second);

return ('12345678901234568.13') <= ('12345678901234568.12');

Related

Why does subtracting decimals not work in javascript [duplicate]

This question already has answers here:
difference between parseInt() and parseFloat() [duplicate]
(2 answers)
Closed 10 months ago.
If I do the code below and enter a decimal for one or both of the numbers, lets says I use 0.5 and 0.3, I should get 0.2 but I get 0 only. This makes no sense at all to me, it is probably a problem with using prompt but I need to use prompt or a method that is similar to prompt(I'm using sweetalert2 input for the alert). I am okay with using any js libraries.
const x = parseInt(prompt('1'))
const y = parseInt(prompt('2'))
alert(x-y)
I know it is a weird problem, but I don't know how to fix it.
You need to use parseFloat, not parseInt. parseInt is whole numbers only, while parseFloat allows decimal places.
parseFloat('0.9') === 0.9
parseInt('0.9') === 0

What's the deal with big number faulty arithematic in JS? [duplicate]

This question already has answers here:
What is JavaScript's highest integer value that a number can go to without losing precision?
(21 answers)
Large numbers erroneously rounded in JavaScript
(6 answers)
javascript large integer round because precision? (why?)
(2 answers)
Closed 1 year ago.
So, I found something I couldn't understand and can't find any internet resource that explains it.
Please see the code below:
var num = 35422484817926290
// subtract 5 from num
console.log(num-5)
Output (Wrong) : 35422484817926284
I checked it in Node, Opera, and Chrome, all of them give the wrong answers.
I do understand the fact that arithmetic with unsafe Integers in JS is faulty, for example:
console.log(100000000000000005-1)
Output (Wrong) : 100000000000000000
So what's the deal with big number arithmetic in JS?
When I run this code:
var num = 35422484817926290
// subtract 5 from num
console.log(num-5)
in Visual Studio Code, i get the following warning:
"Numeric literals with absolute values equal to 2^53 or greater are too large to be represented accurately as integers."
So the correct way to make this calculation would be like this:
var num = 35422484817926290n
// subtract 5 from num
console.log(num-5n)
JavaScript is not faulty, this is how the Floating point arithmetic works. Looks duplicate to this post. For better calculation involving floating-point numbers you should use BigNumber API.

Understanding Javascript parseFloat Behavior [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Is JavaScript’s Floating-Point Math Broken?
Note - I have read other posts on parseFloat(), but I have not found a good explanation as to why the problem occurs. (Or I just didn't understand it).
This code ...
var sum = parseFloat("1.001") + parseFloat(".001");
alert(parseFloat(sum));​
outputs ...
1.0019999999999998
I've read that adding sum.toFixed(2) will include only 2 decimal points.
However, I do not 100% understand why this long decimal occurs.
Does parseFloat(sum) represent sum in binary? If so, then 1.001 cannot be represented in binary since 1/2^x + ... can never equal .001 or 1/1000 exactly?
This isn't specific to Javascript, but rather how IEEE Floating Point Numbers are represented internally that cause precision errors.
I won't reproduce the content here, but there are a bunch of resources available to help explain what is going on in your example.
Here is one: http://www.petebecker.com/js/js200006.html

How do I format numbers into decimal notation? [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Display two decimal places, no rounding
I need to format the total result numbers in 2 decimal format. I am trying to achieve it without using jQuery plugin but just editing my following function:
function tally(selector) {
var total = 0;
$('p.editable_number').each(function() {
total += parseInt($(this).text()) || 0;
$('#subtotal').html(total)
$('#total').html(total*0.21);
$('#total1').html(total*1.21);
})
}
How this is possible modifying the VAR? There are other ways to achieve it?
Here my case, as you can notice i dont get the total result formatted just with decimal separator
$('#subtotal').html((total).toFixed(2))
$('#total').html((total*0.21).toFixed(2));
$('#total1').html((total*1.21).toFixed(2));
One note though: in generic case, where the base is not an integer, it's possible that base + vat != total because of rounding.
If I understand correctly, you want to format your total so that it displays with 2 decimals.
Try this:
$('#subtotal').html(total.toFixed(2));
and so on...
Hope this helps.

How to get 12.6 with a=10.3 and b=2.3? [duplicate]

This question already has answers here:
How to deal with floating point number precision in JavaScript?
(47 answers)
Closed 8 years ago.
Tried :
var a=10.3;
var b=2.3;
alert(a+b);
but I get 12.600000000000001. I know JavaScript is loosely typed, but I hope I can do a sum :)
you can use toFixed() method also
var a=10.3;
var b=2.3;
alert((a+b).toFixed(1));​
Works in chrome
Multiply to the precision you want then round and divide by whatever you multiplied by:
var a=10.3;
var b=2.3;
alert(Math.round((a+b) * 10) / 10);
http://jsfiddle.net/DYKJB/3/
It's not about the typing but about the precision of floating point types. You need to round for presentation.
Floating point types are not a good choice if you need exact values. If you want to express currency values express them as cents or use an appropriate library for this.

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