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How can I handle float number correctly in JS?

In JS, I do have a float number which come from php as below:
var number = 2,206.00
In JS, I need to use parseFloat that number.
So I tried parseFloat(number), but its give only 2. So how can I get 2206.00 instead of 2?

Number.parseFloat is the same function object as globalThis.parseFloat.
If globalThis.parseFloat encounters a character other than:
a plus sign or,
a minus sign or,
a decimal point or,
an exponent (E or e)
...it returns the value up to that character, ignoring the invalid character and characters following it. A second decimal point also stops parsing.
So the following prints 2. And this seems to be your problem.
console.log(parseFloat('2,206.00')) // 2
Solution: use string manipulation to remove any commas from the number (really a String before parsing it.
console.log(parseFloat('2,206.00'.replaceAll(',', ''))) // 2206
If you need to store the value as a number but render it as a formatted string, you may need Number#toFixed to render the values after the decimal point:
console.log((2206).toFixed(2)) // '2206.00'
Final note: be careful about localization because some countries use commas for decimal points and decimal points for number grouping. As #t.niese says: store number values without localization, and then apply localization at the surface of your app. But that is a wider, more complicated topic.

You have to remove comma first and use parseFloat.
And about 2 decimal after dot, I see you use number_format($myNumber, 2) in PHP, so in JS, you use .toFixed(2).
var number = '2,206.00';
var result = parseFloat(number.replace(/,/g, '')).toFixed(2);
console.log(result);

First of all what you currently have most probably would trigger an Unexpected number error in JS.
It seems the generated value comes from the number_format() PHP function which returns a string. Moreover the var number variable should also be considered a string as we have a string format.
So firstly you should quote var number = '2,206.00' after that, you have to make the string float-like in order to parse it as float so we should replace , with empty string in order for the number to become 2206.00 number = number.replace(",",""). Lastly the parse should be done now in order to convert the float-like string to an actual float parseFloat(number).
Whole code:
var number = '2,206.00';
number.replace(",","");
number = parseFloat(number);

ok, basically you want a two decimal number after point like (20.03),
try this
parseFloat(number).toFixed(2)

Parsefloat with 2 decimals without losing function to do equations (not as string)

I've seen multiple topics regarding this question, but none seem to answer it.
I want to round a number to two decimals, but without losing the function to use it in equations. So it shouldn't be transformed to a string. This DOES NOT work for what I want: parseFloat("50").toFixed(2)
Does anyone know how to parseFloat with 2 decimals as a number?

Just parse it back to a float.
parseFloat(Number(1.2345).toFixed(2)); //1.23

In javascript a number cannot have trailing zeros. 2.5 is a correct but 2.50 is not, this is why toFixed returns a string, not a number.
The best way to handle what you need is to store the number as a number and let it round out to whatever it needs. Only when showing the number on the screen should you do the toFixed(2) method to transforms it into a string.
// js
const price = 7.999999
const reducedPrice = price * 0.8
const finalReductionPrice = reducedPrice / 2.666666
// html
<p>price {price.toFixed(2)</p>
<p>reducedPrice {reducedPrice.toFixed(2)</p>
<p>finalReductionPrice {finalReductionPrice.toFixed(2)</p>

parsing string to decimal doesn't return decimals JavaScript

I'm new to writing JavaScript, I'm trying to convert two values from a string to a number, however, I have tried to doing the following approaches but none seem to work.
Example:
const num = parseInt('100.00') // returns 100
const num = Number('100.00') // returns 100
const num = +'100.00'; // returns 100
I need to return 100.00 as a number I have gone to other similar post they didn't seem to help, all knowledge is appreciated thanks!

In Javascript everything is Number, which is double-precision floating point 64 bit number (=decimal).
100.00 is equal to 100, therefore it shows you 100.

What you are asking is not possible, the decimal 100 is not representable as 100.00 as number, you can only represent it as a String with help of toFixed;
var num = 100;
var strNum = num.toFixed(2); // in this case you have a string instead of a number
console.log(typeof num, num);
console.log(typeof strNum, strNum);

It seems to me that all the approaches you have tried work.
Internally, JavaScript stores all numbers using the floating point format. It uses the minimum number of decimals needed when it displays the value.
This is 0 for integer numbers as 100. 100.00 is still 100, adding any number of 0 after the decimal point doesn't change its value.
The recommended method to parse a string that looks like a number is to use Number.parseInt() or Number.parseFloat().
parseFloat() recognizes only numbers written in base 10 but parseInt() attempts to detect the base by analyzing the first characters of the input string. It automatically recognizes numbers written in bases 2, 8, 10 and 16 using the rules described in the documentation page about numbers. This is why it's recommended to always pass the second argument to parseInt() to avoid any ambiguity.
Regarding your concern, use Number.toFixed() to force its representation using a certain number of decimal digits, even when the trailing digits are 0:
const num = parseInt('100.00');
console.log(num); // prints '100'
console.log(num.toFixed(2)); // prints '100.00'

Rounding a figure retrieved from html using javascript and jquery

I am having a little problem with rounding numbers which are brought in from html.
For example a value extracted from <input id="salesValue"> using var salesValue = $("salesValue").val() would give me a text value.
So if I did something like var doubleSalesValue = salesValue + salesValue; , it would return the number as a concatenation instead of summation of the two values.
I could use var doubleSalesValue = salesValue * 2.0; which does return the value which is to multiple decimal places. However, if I did want to use the other method, how can I approach the situation.
What methods do you use? I have created a function which I run on each number where I want to restrict the decimal places along with converting the type to number
function round(number, figure){
return Number(Number(number).toFixed(figure));
}
I have to run Number initially to make sure that the value is converted to type number and has the method toFixed, otherwise it would throw an error here. Then I have to round the number again to the number of decimal places as required by the function, and somehow after running the toFixed method the number would sometimes turn to a string.
So, I decided to run the Number function Number(number).toFixed(figure)
Is there anything else or any different paradigm that you follow?
EDIT: I want to know if what I am doing here is conventional or are there better methods for this in general?

If you want to round it to 2 decimals you can simply do this:
var roundedNum = Math.round(parseFloat(originalNum) * 100) / 100;
Regarding your question:
and somehow after running the toFixed method the number would sometimes turn to a string.
I suggest next time read the dox a bit better https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed which says:
Returns
A string representation of number that does not use exponential
notation and has exactly digits digits after the decimal place. The
number is rounded if necessary, and the fractional part is padded with
zeros if necessary so that it has the specified length. If number is
greater than 1e+21, this method simply calls
Number.prototype.toString() and returns a string in exponential
notation.

whole number in javascript?

I get 28.6813276578 when i multiply 2 numbers a and b, how can i make it whole number with less digits
and also, when i multiply again i get results after first reult like 28.681321405.4428.68 how to get only one result ?
<script>
$(document).ready(function(){
$("#total").hide();
$("#form1").submit(function(){
var a = parseFloat($("#user_price").val());
var b = parseFloat($("#selling").val());
var total = a*b;
$("#total").append(total)
.show('slow')
.css({"background":"yellow","font-size":50})
;
return false;
});
});
</script>

You can do several things:
total = total.toFixed([number of decimals]);
total = Math.round(total);
total = parseInt(total);
toFixed() will round your number to the number of decimals indicated.
Math.round() will round numbers to the nearest integer.
parseInt() will take a string and attempt to parse an integer from it without rounding. parseInt() is a little trickier though, in that it will parse the first characters in a string that are numbers until they are not, meaning parseInt('123g32ksj') will return 123, whereas parseInt('sdjgg123') will return NaN.
For the sake of completeness, parseInt() accepts a second parameter which can be used to express the base you're trying to extract with, meaning that, for instance,
parseInt('A', 16) === 10 if you were trying to parse a hexidecimal.

See Math.round(...).
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Math/round

In addition to the other answers about rounding, you are appending the answer to "total" by using
$("#total").append(total)
You need to replace the previous text rather than appending by using
$("#total").html(total)