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How to make a number from string with comma separators in JavaScript ("23,21" ---> 23,21)

Does anyone know how to make a number from a string with comma separators, in JS.
I got: "23,21" and I want to get it as a number value.
"23,21" --> 23,21

You can use https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat
But before you need to replace comma for dot.
parseFloat('23,21'.replace(/,/, '.')); // == 23.21
let x = '16,5';
parseFloat(x.replace(/,/, '.')); // == 16.5

You can but not with the "comma" (,). In some countries people do use commas instead of dots to write decimals. If that's the case then what you can do is:
let a = "23,25";
let b = a.replaceAll(',', '.');
console.log(parseFloat(b));
But doing the this with the comma is also not wrong. But you will only get the part before the decimal.
i.e. 23 in your case

Check if you want this.
var str = '23,21';
console.log((str.split(",").map((i) => Number(i))));
UPDATE
var str = '23,21';
var arr = str.split(",").map((i) => Number(i));
console.log(parseFloat(arr.join('.')));

I need help getting the first n characters of a string up to when a number character starts

I'm working with a string where I need to extract the first n characters up to where numbers begin. What would be the best way to do this as sometimes the string starts with a number: 7EUSA8889er898 I would need to extract 7EUSA But other string examples would be SWFX74849948, I would need to extract SWFX from that string.
Not sure how to do this with regex my limited knowledge is blocking me at this point:
^(\w{4}) that just gets me the first four characters but I don't really have a stopping point as sometimes the string could be somelongstring292894830982 which would require me to get somelongstring

Using \w will match a word character which includes characters and digits and an underscore.
You could match an optional digit [0-9]? from the start of the string ^and then match 1+ times A-Za-z
^[0-9]?[A-Za-z]+
Regex demo
const regex = /^[0-9]?[A-Za-z]+/;
[
"7EUSA8889er898",
"somelongstring292894830982",
"SWFX74849948"
].forEach(s => console.log(s.match(regex)[0]));

Can use this regex code:
(^\d+?[a-zA-Z]+)|(^\d+|[a-zA-Z]+)
I try with exmaple and good worked:
1- somelongstring292894830982 -> somelongstring
2- 7sdfsdf5456 -> 7sdfsdf
3- 875werwer54556 -> 875werwer

If you want to create function where the RegExp is parametrized by n parameter, this would be
function getStr(str,n) {
var pattern = "\\d?\\w{0,"+n+"}";
var reg = new RegExp(pattern);
var result = reg.exec(str);
if(result[0]) return result[0].substr(0,n);
}

There are answers to this but here is another way to do it.
var string1 = '7EUSA8889er898';
var string2 = 'SWFX74849948';
var Extract = function (args) {
var C = args.split(''); // Split string in array
var NI = []; // Store indexes of all numbers
// Loop through list -> if char is a number add its index
C.map(function (I) { return /^\d+$/.test(I) === true ? NI.push(C.indexOf(I)) : ''; });
// Get the items between the first and second occurence of a number
return C.slice(NI[0] === 0 ? NI[0] + 1 : 0, NI[1]).join('');
};
console.log(Extract(string1));
console.log(Extract(string2));
Output
EUSA
SWFX7

Since it's hard to tell what you are trying to match, I'd go with a general regex
^\d?\D+(?=\d)

split string based on a symbol

I'm trying to split a string into an array based on the second occurrence of the symbol _
var string = "this_is_my_string";
I want to split the string after the second underscore. The string is not always the same but it always has 2 or more underscores in it. I always need it split on the second underscore.
In the example string above I would need it to be split like this.
var split = [this_is, _my_string];

var string = "this_is_my_string";
var firstUnderscore = string.indexOf('_');
var secondUnderscore = string.indexOf('_', firstUnderscore + 1);
var split = [string.substring(0, secondUnderscore),
string.substring(secondUnderscore)];
Paste it into your browser's console to try it out. No need for a jsFiddle.

var string = "this_is_my_string";
var splitChar = string.indexOf('_', string.indexOf('_') + 1);
var result = [string.substring(0, splitChar),
string.substring(splitChar, string.length)];
This should work.

var str = "this_is_my_string";
var matches = str.match(/(.*?_.*?)(_.*)/); // MAGIC HAPPENS HERE
var firstPart = matches[1]; // this_is
var secondPart = matches[2]; // _my_string
This uses regular expressions to find the first two underscores, and captures the part up to it and the part after it. The first subexpression, (.*?_.*?), says "any number of characters, an underscore, and again any number of characters, keeping the number of characters matched as small as possible, and capture it". The second one, (_.*) means "match an underscore, then any number of characters, as much of them as possible, and capture it". The result of the match function is an array starting with the full matched region, followed by the two captured groups.

I know this post is quite old... but couldn't help but notice that no one provided a working solution. Here's one that works:
String str = "this_is_my_string";
String undScore1 = str.split("_")[0];
String undScore2 = str.split("_")[1];
String bothUndScores = undScore1 + "_" + undScore2 + "_";
String allElse = str.split(bothUndScores)[1];
System.out.println(allElse);
This is assuming you know there will always be at least 2 underscores - "allElse" returns everything after the second occurrence.

regex to get the number from the end of a string

i have a id like stringNumber variable like the one as follows : example12
I need some javascript regex to extract 12 from the string."example" will be constant for all id and just the number will be different.

This regular expression matches numbers at the end of the string.
var matches = str.match(/\d+$/);
It will return an Array with its 0th element the match, if successful. Otherwise, it will return null.
Before accessing the 0 member, ensure the match was made.
if (matches) {
number = matches[0];
}
jsFiddle.
If you must have it as a Number, you can use a function to convert it, such as parseInt().
number = parseInt(number, 10);

RegEx:
var str = "example12";
parseInt(str.match(/\d+$/)[0], 10);
String manipulation:
var str = "example12",
prefix = "example";
parseInt(str.substring(prefix.length), 10);

Separate character and number in javascript

I have one string which contain number and character. I need to separate number and character. I have don't have a delimiter in between. How can I do this.
Var selectedRow = "E0";
I need to "0" in another variable.
Help me on this.

Depends on the format of the selected row, if it is always the format 1char1number (E0,E1....E34) then you can do:
var row = "E0";
var rowChar = row.substring(0, 1);
// Number var is string format, use parseInt() if you need to do any maths on it
var number = row.substring(1, row.length);
//var number = parseInt(row.substring(1, row.length));
If however you can have more than 1 character, for example (E0,E34,EC5,EDD123) then you can use regular expressions to match the numeric and alpha parts of the string, or loop each character in the string.

var m = /\D+(\d+)/gi.exec(selectedRow);
var row = m.length == 2 ? m[1] : -1;

selectedRow.charAt(1)
Becomes more complex if your example is something longer than 'E0', obviously.