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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)

regex to ignore special characters

Say, I have a text stored as:
var val1 = 'l-oreal';
I want to match val1 such that, it reads val1 and ignores hyphen (dash) in it. I want a regex that ignores special characters in a text. Is that possible?
I don't want to remove special character from the text. I want to ignore it.

You can match against the regex /[a-z]+/gi and then join by a space or any other character:
var testString = "any string l-orem";
var matcher = /[a-z]+/gi;
var matches = testString.match(matcher);
var result = matches.join('');
console.log(result);
This, of course, doesn't change your original string, and can be simply customized to your own needs.

You can either use ^ in order to select your special characters then replace it to an empty string '', as:
val1.replace(/([^a-zA-z0-9]+)/g, s0 => ''); // loreal
All except a-zA-Z-0-9 will be removed.
Updated post for scenario when:
The string must contain characters abc and ignore any special
characters
for this approach, you could make use of match to know if your string has any matches on your regex. If so, then you could use replace to switch special chars to empty string:
function strChecker(str) {
var response;
if(val1.match(/lorem/)) {
response = val1.replace(/([^a-zA-z0-9]+)/g, s0 => '');
}
return response;
}
strChecker('ha-ha?lorem') // returns hahalorem
strChecker('ha-ha?loram') // return undefined

var val1 = 'l-oreal';
var val2 = val1.replace(/\W/g,''); // remove any non-alphanumerics
console.log(val1); // still the same, not changed
console.log(val2); // only alphanumerics

Javascript Regular Expression for numbers

I am trying to make a HTML form that accepts a rating through an input field from the user. The rating is to be a number from 0-10, and I want it to allow up to two decimal places. I am trying to use regular expression, with the following
function isRatingGood()
{
var rating = document.getElementById("rating").value;
var ratingpattern = new RegExp("^[0-9](\.[0-9][0-9]?)?$");
if(ratingpattern.test(rating))
{
alert("Rating Successfully Inputted");
return true;
}
else
{
return rating === "10" || rating === "10.0" || rating === "10.00";
}
}
However, when I enter any 4 or 3 digit number into the field, it still works. It outputs the alert, so I know it is the regular expression that is failing. 5 digit numbers do not work. I used this previous answer as a basis, but it is not working properly for me.
My current understanding is that the beginning of the expression should be a digit, then optionally, a decimal place followed by 1 or 2 digits should be accepted.

You are using a string literal to created the regex. Inside a string literal, \ is the escape character. The string literal
"^[0-9](\.[0-9][0-9]?)?$"
produces the value (and regex):
^[0-9](.[0-9][0-9]?)?$
(you can verify that by entering the string literal in your browser's console)
\. is not valid escape sequence in a string literal, hence the backslash is ignored. Here is similar example:
> "foo\:bar"
"foo:bar"
So you can see above, the . is not escaped in the regex, hence it keeps its special meaning and matches any character. Either escape the backslash in the string literal to create a literal \:
> "^[0-9](\\.[0-9][0-9]?)?$"
"^[0-9](\.[0-9][0-9]?)?$"
or use a regex literal:
/^[0-9](\.[0-9][0-9]?)?$/

The regular expression you're using will parsed to
/^[0-9](.[0-9][0-9]?)?$/
Here . will match any character except newline.
To make it match the . literal, you need to add an extra \ for escaping the \.
var ratingpattern = new RegExp("^[0-9](\\.[0-9][0-9]?)?$");
Or, you can simply use
var ratingPattern = /^[0-9](\.[0-9][0-9]?)?$/;
You can also use \d instead of the class [0-9].
var ratingPattern = /^\d(\.\d{1,2})?$/;
Demo
var ratingpattern = new RegExp("^[0-9](\\.[0-9][0-9]?)?$");
function isRatingGood() {
var rating = document.getElementById("rating").value;
if (ratingpattern.test(rating)) {
alert("Rating Successfully Inputted");
return true;
} else {
return rating === "10" || rating === "10.0" || rating === "10.00";
}
}
<input type="text" id="rating" />
<button onclick="isRatingGood()">Check</button>

Below find a regex candidate for your task:
^[0-1]?\d(\.\d{0,2})?$
Demo with explanation
var list = ['03.003', '05.05', '9.01', '10', '10.05', '100', '1', '2.', '2.12'];
var regex = /^[0-1]?\d(\.\d{0,2})?$/;
for (var index in list) {
var str = list[index];
var match = regex.test(str);
console.log(str + ' : ' + match);
}

This should also do the job. You don't need to escape dots from inside the square brackets:
^((10|\d{1})|\d{1}[.]\d{1,2})$
Also if you want have max rating 10 use
10| ---- accept 10
\d{1})| ---- accept whole numbers from 0-9 replace \d with [1-9]{1} if don't want 0 in this
\d{1}[.]\d{1,2} ---- accept number with two or one numbers after the coma from 0 to 9
LIVE DEMO: https://regex101.com/r/hY5tG4/7
Any character except ^-]\ All characters except the listed special characters are literal characters that add themselves to the character class. [abc] matches a, b or c literal characters

Just answered this myself.
Need to add square brackets to the decimal point, so the regular expression looks like
var ratingpattern = new RegExp("^[0-9]([\.][0-9][0-9]?)?$");

Javascript extract numbers from a string

I want to extract numbers from a string in javascript like following :
if the string = 'make1to6' i would like to extract the numeric character before and after the 'to' substring in the entire string. i.e. 1 and 6 are to be extracted
The length of the string is not fixed and can be a max of 10 characters in length.The number can be of max two digits on either side of 'to' in the string.
Possible string values :
sure1to3
ic3to9ltd
anna1to6
joy1to4val
make6to12
ext12to36
thinking of something like :
function beforeTo(string) {
return numeric_value_before_'to'_in_the_string;
}
function afterTo(string) {
eturn numeric_value_after_'to'_in_the_string;
}
i will be using these returned values for some calculations.

Here's an example function that will return an array representing the two numbers, or null if there wasn't a match:
function extractNumbers(str) {
var m = /(\d+)to(\d+)/.exec(str);
return m ? [+m[1], +m[2]] : null;
}
You can adapt that regular expression to suit your needs, say by making it case-insensitive: /(\d+)to(\d+)/i.exec(str).

You can use a regular expression to find it:
var str = "sure1to3";
var matches = str.match(/(\d+)to(\d+)/);
if (matches) {
// matches[1] = digits of first number
// matches[2] = digits of second number
}

What's a good RegExp that will strip out all characters except Integers from a string?

I'm new to using regexp, can someone give me the regexp that will strip out everything but an integer from a string in javascript?
I would like to take the string "http://www.foo.com/something/1234/somethingelse" and get it down to 1234 as an integer.
Thanks

var str = "something 123 foo 432";
// Replace all non-digits:
str = str.replace(/\D/g, '');
alert(str); // alerts "123432"
In response to your edited question, extracting a string of digits from a string can be simple, depending on whether you want to target a specific area of the string or if you simply want to extract the first-occurring string of digits. Try this:
var url = "http://www.foo.com/something/1234/somethingelse";
var digitMatch = url.match(/\d+/); // matches one or more digits
alert(digitMatch[0]); // alerts "1234"
// or:
var url = "http://x/y/1234/z/456/v/890";
var digitMatch = url.match(/\d+/g); // matches one or more digits [global search]
digitMatch; // => ['1234', '456', '890']

This is just for integers:
[0-9]+
The + means match 1 or more, and the [0-9] means match any character from the range 0 to 9.

uri = "http://www.foo.com/something/1234/somethingelse";
alert(uri.replace(/.+?\/(\d+)\/.+/, "$1"))

Just define a character-class that requires the values to be numbers.
/[^0-9]/g // matches anything that is NOT 0-9 (only numbers will remain)