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Javascript: GUID: RegEx: string to GUID

I have a textbox that a user can paste into using Ctrl+V. I would like to restrict the textbox to accept just GUIDs. I tried to write a small function that would format an input string to a GUID based on RegEx, but I can't seem to be able to do it. I tried following the below post:
Javascript string to Guid
function stringToGUID()
{
var strInput = 'b6b954d9cbac4b18b0d5a0f725695f1ca98d64e456f76';
var strOutput = strInput.replace(/([0-f]{8})([0-f]{4})([0-f]{4})([0-f]{4})([0-f]{12})/,"$1-$2-$3-$4-$5");
console.log(strOutput );
//from my understanding, the input string could be any sequence of 0-9 or a-f of any length and a valid giud patterened string would be the result in the above code. This doesn't seem to be the case;
//I would like to extract first 32 characters; how do I do that?
}

I suggest that you remove the dashes, truncate to 32 characters, and then test if the remaining characters are valid before inserting the dashes:
function stringToGUID()
{
var input = 'b6b954d9cbac4b18b0d5a0f725695f1ca98d64e456f76';
let g = input.replace("-", "");
g = g.substring(0, 32);
if (/^[0-9A-F]{32}$/i.test(g)) {
g = g.replace(/(.{8})(.{4})(.{4})(.{4})(.{12})/, "$1-$2-$3-$4-$5");
}
console.log(g);
}
stringToGUID();
(The i at the end of the regex makes it case-insensitive.)

You are already matching 32 characters with the pattern, so there is no need to get a separate operation to get 32 characters to test against.
You can replace all the hyphens with an empty string, and then match the pattern from the start of the string using ^
Then first check if there is a match, and if there is do the replacement with the 5 groups and hyphens in between. If there is not match, return the original string.
The function stringToGUID() by itself does not do anything except log a string that is hardcoded in the function. To extend its functionality, you can pass a parameter.
function stringToGUID(s) {
const regex = /^([0-f]{8})([0-f]{4})([0-f]{4})([0-f]{4})([0-f]{12})/;
const m = s.replace(/-+/g, '').match(regex);
return m ? `${m[1]}-${m[2]}-${m[3]}-${m[4]}-${m[5]}` : s;
}
[
'b6b954d9cbac4b18b0d5a0f725695f1ca98d64e456f76',
'b6b954d9-cbac-4b18-b0d5-a0f725695f1c',
'----54d9cbac4b18b0d5a0f725695f1ca98d64e456f76',
'!##$%'
].forEach(s => {
console.log(stringToGUID(s));
});

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)

Number and Alphabet Separation in a String

I have String variables in Javascript like :
var houseNo = "62A"; var cabinNo = "5BC";
I need to fetch out the Integers and the Alphabets separate from the string where number of occurrences of each can be any number of times.
Need help to do it in the best possible way, be it through lodash or any other prototype method.
Referred to this but left in vain as don't want it through RegEx.

something like :
function decompose(string){
for(var i=0;i<string.length;i++){
if(parseInt(string[i])){ // if the char is a number?
// do whatever you want
}else{
// it's a character
}
}
}
The parseInt() function return the number of a giver char. If it is not a number, it returns NaN (not a number). if(parsInt(char)) return false if it's a char, true if it's a number

Try this:
var houseNo = "62A";
foreach(char a in houseNo)
{
if(a > 48 && a < 57)
{
/*it's a number*/
}
else
{
/*it's a letter*/
}
}
You can apply it on every string and determine what you want to do with each number or letter.

var test = "a3434dasds3432s2"
var myString = test.split("").filter(function(v) {return isNaN(v)}).join("")
var myNumber = parseInt(test.split("").filter(function(v) {return !isNaN(v)}).join(""))
best to use regex really though.

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.