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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)

Which javascript function can be used to covert an array of characters into a number?

There are a few Javascript functions available to convert anything into its equivalent number. Number() operates on an Object, valueOf(), parseFloat, parseInt() are also available.
I have an array which stores numbers 0-9 and decimal point, the elements of the array taken together represents a number. What is the best way to convert this array into a number, whole or fractional?
EDIT: Apologies if I were not clear before. The array, holding the 0-9 characters and possibly a decimal point, could represent either a whole number(without the decimal obviously) or a fractional number. So please suggest something that works for both cases. Thanks.

Try this
var a = [1,2,3,".",2,3];
var num = +a.join("");

What is the best way to convert this array into a number, whole or fractional?
Firstly to combine your array elements you should use Array.join().
You will then have a concatenated variable of your values and decimal. To convert this to a whole number, use parseInt(), and to a floating point number use parseFloat(). You can use the unary + operator (which acts similarly to parseFloat), however in my opinion it is not the best choice semantically here, as you seem to want a specific type of number returned.
Example:
var arr = ['1','.','9','1'];
var concat = arr.join();
var whole = parseInt(concat);
var floating = parseFloat(concat);
Also, parseInt will trim the decimal portion of your number, so if you need rounding you can use:
var rounded = Math.round(parseFloat(concat));

You could use the split property of the string. It splits all the characters into an zero based array.
var charSplits = "this is getting split.";
var splitArr = charSplits.split();
Console.log(splitArr);
// this returns i
Console.log(splitArr[2]);

Why does my textarea (HTML) value show 12,000,000.11 but after parseFloat the value is only 12?

I am attempting to develop a conversion website that takes a numeric value:
1,200.12
or
1.200,12
or
1200.12
or
1200,12
and have them all interpreted as 1200.12 by parseFloat.
I would also like decimals to be able to be interpreted.
0.123
or
0,123
as 0.123
through a textarea and then parseFloat the number in order to perform calculations.
These are the results I am getting:
textarea input = 12,000.12
value after parseFloat = 12
Does parseFloat not recognize the formatting of the numbers?
i get the same results with:
textarea input: 12.000,12
value after parseFloat = 12
How do I solve this problem? It would seem I need to strip out the commas since parseFloat doesn't read beyond them and with european notation strip the decimals and change the comma to a decimal for parseFloat to read the input correctly. Any ideas on how to solve this? My guess is I would need to identify the string input as either european or american decimal notation and then perform the required actions to prepare the string for parseFloat. How would I go about achieving that? All contributions are appreciated. Using HTML5 and Javascript. This is my first website so please go easy on me.
Best,
RP
To all contributors...Thank you! So far all the input has been sweet. I don't think we are going to be able to use a single replace statement to correctly strip both european and american notation so I think I should use REGEX somehow to determine the notation and then split into an if else statement to perform separate replace functions on each individual notation.
var input, trim;
input = "1.234,56" //string from textarea on page
if(/REGEX that determines American Notation/.test(input){
trim = input.replace(/\,/,"");//removes commas and leaves decimal point);
}
else(/REGEX that determine European Notation/.test(input)/){ //would qualify input here
rep = input.replace(/\./,"");//removes all decimal points);
trim = rep.replace(/\,/,"."//changes the remaining comma to a decimal);
}
//now either notation should be in the appropriate form to parse
number = parseFloat(trim);
Is this possible using REGEX? Please see my other question.
Regex - creating an input/textarea that correctly interprets numbers

One way would be to strip the comma signs, for example with:
.replace(",", "")
From there you should be able to parseFloat
Updated with fiddle: http://jsfiddle.net/aLv74xpu/2/

Here is a solution that uses a regular expression to eliminate all commas and all periods, except the last one.
var number = "1,234.567.890";
var replaced = number.replace(/,|\.(?=.*\.)/g, "");
var result = parseFloat(replaced);
// result === 1234567.89
Alternatively, you can use this, which treats commas and periods identically, and ignores them all except for the last one.
var number = "12.345,67";
var replaced = number.replace(/[.,](?=.*[.,])/g, "").replace(",", ".");
var result = parseFloat(replaced);
// result === 12345.67

parseFloat parses its argument, a string, and returns a floating point
number. If it encounters a character other than a sign (+ or -),
numeral (0-9), a decimal point, or an exponent, it returns the value
up to that point and ignores that character and all succeeding
characters. Leading and trailing spaces are allowed.
From the good MDN network: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat
So it is the expected behaviour of parseFloat

correct number format detection separator

I have
var value = $120,90
var value = $1,209.00
currently I replace the first case with
value = value.replaceAll(",", ".").replaceAll("[^0-9.]*", "");
which gives me that I am looking for: the integer 12090
with the second case I run in a problem however like this. How can I solve this in Javascript?

You may modify you regexp.
value = value.replace(/,/g, ".").replace(/^\D|\.(?!\d*$)/g, "");
First will replace ',' to '.' and the 2nd replace NON-digit symbols in the beginning of the string and all dots EXCEPT the last one with the empty string. Then use parseFloat.
To be sure completely it's better to create a template for data input and don't allow users to enter values in an invalid format.

I cannot see how you can make an algorithm work unless you insist that everyone enters dollars and cents. The only option I can think of is to use locale to determine the number separator.

Could you use the answer from this thread?
How can I remove the decimal part from JavaScript number?
They use Math.floor() (round down), Math.ceil() (round up) or Math.round() (round to nearest integer).

JavaScript treats numbers as strings, not integers, and ParseInt doesn't fix it

I'm trying to insert two numbers in two input type text fields. After I do that, I have to make sure than the first number is smaller than the second. To do this, I'm capturing both fields like this:
var supt = $('#suptotal').val();
var supc = $('#supcubierta').val();
When I compare the two variables, they are strings, so for example 21 is considered bigger than 123.
I've tried to use the function ParseInt, like this
var supt = ParseInt($('#suptotal').val());
but it didn't work. How can I compare the numbers as numbers?

use parseInt($('#suptotal').val(), 10) as against ParseInt($('#suptotal').val(), 10)
The function names are case sensitive

parseInt( $('#suptotal').val(), 10 );
Specify a radix as well, incase the string contains something like '010' which would be interpreted as an octal and result in 8.

ParseInt($('#suptotal').val());
You've written the function incorrectly. parseInt is defined in a lowerCamelCase style.
parseInt($('#suptotal').val());
It is also advised that you specify the radix parameter with 10 for base 10.
parseInt($('#suptotal').val(), 10);
But if you are simply wanting to convert the string into a number, use the unary effect of the binary operator +, which will coerce a value into a number when used on a single operand:
var supt = +$('#suptotal').val();