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Replace multiple strings containing $ sign

I face a problem with regex and string replace and I would love a little bit of help.
I have a string with the following format
<div class="$(unique-result) single-result data-index=$(i)"><div class="airport-data data-index=$(i)">$(name)<br>$(city) ,$(country)</div><div class="airport-code data-index=$(i)">$(IATA)</div></div>
and I need to replace all the $(unique-result) with a string of mine.
I tried the following code but I can't seem to find out why this doesn't work
string.replace(new RegExp('\\$(unique-result)', 'g'), changeString)
The result is the exact same string I gave as an input.
Could anyone help me out but also point out why it didn't work?
Thank you in advance.

You missed escaping. you need to escape properly
let str = `<div class="$(unique-result) single-result data-index=$(i)"><div class="airport-data data-index=$(i)">$(name)<br>$(city) ,$(country)</div><div class="airport-code data-index=$(i)">$(IATA)</div></div>`
let op = str.replace(new RegExp('\\$\\(unique-result\\)','g'), 'Changed')
console.log(op)
In case i am not using any variable i prefer using regex literal (//)
let str = `<div class="$(unique-result) single-result data-index=$(i)"><div class="airport-data data-index=$(i)">$(name)<br>$(city) ,$(country)</div><div class="airport-code data-index=$(i)">$(IATA)</div></div>`
let op = str.replace(/\$\(unique-result\)/g, 'Changed')
console.log(op)

There is more general solution.
First of all, as I mentioned in comments, you don't need to use the RegExp constructor, you can simply pass your regexp between slashes and use flags after last slash:
str.replace(/\$\(unique-result\)/g, "someValue")
The second moment is that String.prototype.replace can accept a function as a second parameter. This will be helpful when there is a lot of named templates in you string. For example, you have the next incoming string:
var incomingString = "$(first-value) says $(second-value) when there is $(third-value)"
With code that you've provided you should call replace 3 times. But if you will use a function as a second parameter, this can be simplified to:
var incomingString = "$(first-value) says $(second-value) when there is $(third-value)"
var data = {
"first-value": "Kappa",
"second-value": "Hey!",
"third-value": "GreyFaceNoSpace"
}
var resultString = incomingString.replace(/\$\(([^)]+)\)/g, (match, capture) => {
console.log(match, capture)
return data[capture]
})
console.log(resultString)
"WHAT IS GOING ON HERE?!" you will probably ask. Nothing complex.
Function that is passed as argument accepts one or more arguments: first is a full match and the others are captured groups. It should return the string, that should replace the full match.
In our regular expression we described that we want to match all possible substrings in format \$\(([^)]+)\), where [^)]+ refers to one-or-more-of-any-symbols-except-a-closing-bracket, and this construction should be captured (it is between not-sanitized brackets).
So, once this regexp will match, it will pass the whole $(...) construction into match argument of passed function, and the name of the template into capture argument. So capture is our key for some data storage and we just returning this value in the function.
That's it! Hope, this will be helpful :)

You can use a simple function to make the substitution. Match every $(string) and apply a function to replace it with a variable stored in an object. Easy and extensible.
const tpl = '<div class="$(unique-result) single-result data-index=$(i)"><div class="airport-data data-index=$(i)">$(name)<br>$(city) ,$(country)</div><div class="airport-code data-index=$(i)">$(IATA)</div></div>';
const vars = {
i : 9,
'unique-result' : 'uniq',
country : 'gb',
city : 'Manchester',
IATA : 'MCH'
};
const replaceVars = (tpl,vars) => {
const replacer = (m, m1) =>
typeof vars[m1] != 'undefined' ? vars[m1] : '';
return tpl.replace(/\$\(([\w-]+)\)/g, replacer);
};
console.log(replaceVars(tpl,vars));

JavaScript split() using a common character then join() using different characters

Assuming I have a string: /someFolder/anotherFolder/fileName and I want to replace all the forward slashes with a "+" then this would work:
var someString = '/someFolder/anotherFolder/fileName'
someString.split('/').join('+');
Or using regex, this would work:
var someString = '/someFolder/anotherFolder/fileName'
someString.replace(/\//g, "+");
But what would be the best approach if I want to replace the first occurence with a '+' then the second occurence with another character like say, the '-', the third with '*' and so on so that the string someString above returns:
+someFolder-anotherFolder*fileName

You can pass a function to replace():
let someString = "/someFolder/anotherFolder/file";
const repl = [ '+', '-', '*' ];
let i = 0;
console.log(someString.replace(/\//g, (match) => repl[(i++) % repl.length]));

You could use an index and a string for getting the wanted character as a closure or take an array if you have more than one character.
var someString = '/someFolder/anotherFolder/fileName'
console.log(someString.replace(/\//g, (i => _ => "+-*"[i++])(0)));

You can use reduce method by passing an arrow function as argument.
var someString = '/someFolder/anotherFolder/fileName'
someString = someString.split('/').slice(1).reduce((str, item, index) => str + "+-*"[index] + item, "");
console.log(someString);

You may chain several String#replace() method calls with a literal string as the search argument to achieve what you need:
var someString = '/someFolder/anotherFolder/fileName';
console.log(someString.replace('/', '+').replace('/', '-').replace('/', '*'));
The point here is that non-regex search argument makes it find the first occurrence only, and since you have three different replacement strings (+, - and *) it is not quite convenient/straight forward to use a regex.

Using RegExp to substring a string at the position of a special character

Suppose I have a sting like this: ABC5DEF/G or it might be ABC5DEF-15 or even just ABC5DEF, it could be shorter AB7F, or AB7FG/H.
I need to create a javascript variable that contains the substring only up to the '/' or the '-'. I would really like to use an array of values to break at. I thought maybe to try something like this.
...
var srcMark = array( '/', '-' );
var whereAt = new RegExp(srcMark.join('|')).test.str;
alert("whereAt= "+whereAt);
...
But this returns an error: ReferenceError: Can't find variable: array
I suspect I'm defining my array incorrectly but trying a number of other things I've been no more successful.
What am I doing wrong?

Arrays aren't defined like that in JavaScript, the easiest way to define it would be with:
var srcMark = ['/','-'];
Additionally, test is a function so it must be called as such:
whereAt = new RegExp(srcMark.join('|')).test(str);
Note that test won't actually tell you where, as your variable suggests, it will return true or false. If you want to find where the character is, use String.prototype.search:
str.search(new RegExp(srcMark.join('|'));
Hope that helps.

You need to use the split method:
var srcMark = Array.join(['-','/'],'|'); // "-|/" or
var regEx = new RegExp(srcMark,'g'); // /-|\//g
var substring = "222-22".split(regEx)[0] // "222"
"ABC5DEF/G".split(regEx)[0] // "ABC5DEF"

From whatever i could understand from your question, using this RegExp /[/-]/ in split() function will work.
EDIT:
For splitting the string at all special characters you can use new RegExp(/[^a-zA-Z0-9]/) in split() function.
var arr = "ABC5DEF/G";
var ans = arr.split(/[/-]/);
console.log(ans[0]);
arr = "ABC5DEF-15";
ans = arr.split(/[/-]/);
console.log(ans[0]);
// For all special characters
arr = "AB7FG/H";
ans = arr.split(new RegExp(/[^a-zA-Z0-9]/));
console.log(ans[0]);

You can use regex with String.split.
It will look something like that:
var result = ['ABC5DEF/G',
'ABC5DEF-15',
'ABC5DEF',
'AB7F',
'AB7FG/H'
].map((item) => item.split(/\W+/));
console.log(result);
That will create an Array with all the parts of the string, so each item[0] will contain the text till the / or - or nothing.

If you want the position of the special character (non-alpha-numeric) you can use a Regular Expression that matches any character that is not a word character from the basic Latin alphabet. Equivalent to [^A-Za-z0-9_], that is: \W
var pattern = /\W/;
var text = 'ABC5DEF/G';
var match = pattern.exec(text);
var position = match.index;
console.log('character: ', match[0]);
console.log('position: ', position);

Javascript match() string letters which are indicated on regular expression of match

I have a variable which contain a string and I want to return only the letters from regular expression (“b” and “D”) or any letter that I indicate on regular expression from match().
var kk = "AaBbCcDd".match(/b|D/g);
kk.forEach(function(value,index){
console.log(value,index)
});
My problem is that regular expression I think because is returning b and D but the index is not the index from kk variable and I'm not really sure, why ... so if someone can help me a little bit because I stuck

The match method from javascript only returns an array with the given match:
https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/match
You would need to implement a new function which will loop through all characters of your string and return the given index of the matches.
This method could use the function search from String.prototype: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/search

You have to write a new function to get the index of the matched regex like a sample below:-
var re = /bar/g,
str = "foobarfoobar";
while ((match = re.exec(str)) != null) {
alert("match found at " + match.index);
}
Hope this will help you

Actually this is the answer :
var kk = "AaBbCcDd".match(/B?d?/g);
kk.forEach(function(value,index){
console.log(value,index)
});
if someone will encounter this scenario ...
The match() regular expresion B?d? will return an array indicating the position of "B" and "d" of the initial array kk.

Javascript convert PascalCase to underscore_case/snake_case

How can I convert PascalCase string into underscore_case/snake_case string? I need to convert dots into underscores as well.
eg. convert
TypeOfData.AlphaBeta
into
type_of_data_alpha_beta

You could try the below steps.
Capture all the uppercase letters and also match the preceding optional dot character.
Then convert the captured uppercase letters to lowercase and then return back to replace function with an _ as preceding character. This will be achieved by using anonymous function in the replacement part.
This would replace the starting uppercase letter to _ + lowercase_letter.
Finally removing the starting underscore will give you the desired output.
var s = 'TypeOfData.AlphaBeta';
console.log(s.replace(/(?:^|\.?)([A-Z])/g, function (x,y){return "_" + y.toLowerCase()}).replace(/^_/, ""));
OR
var s = 'TypeOfData.AlphaBeta';
alert(s.replace(/\.?([A-Z])/g, function (x,y){return "_" + y.toLowerCase()}).replace(/^_/, ""));
any way to stop it for when a whole word is in uppercase. eg. MotorRPM into motor_rpm instead of motor_r_p_m? or BatteryAAA into battery_aaa instead of battery_a_a_a?
var s = 'MotorRMP';
alert(s.replace(/\.?([A-Z]+)/g, function (x,y){return "_" + y.toLowerCase()}).replace(/^_/, ""));

str.split(/\.?(?=[A-Z])/).join('_').toLowerCase();
u're welcome
var s1 = 'someTextHere';
var s2 = 'SomeTextHere';
var s3 = 'TypeOfData.AlphaBeta';
var o1 = s1.split(/\.?(?=[A-Z])/).join('_').toLowerCase();
var o2 = s2.split(/\.?(?=[A-Z])/).join('_').toLowerCase();
var o3 = s3.split(/\.?(?=[A-Z])/).join('_').toLowerCase();
console.log(o1);
console.log(o2);
console.log(o3);

Alternatively using lodash:
lodash.snakeCase(str);
Example:
_.snakeCase('TypeOfData.AlphaBeta');
// ➜ 'type_of_data_alpha_beta'
Lodash is a fine library to give shortcut to many everyday js tasks.There are many other similar string manipulation functions such as camelCase, kebabCase etc.

This solution solves the non-trailing acronym issue with the solutions above
I ported the code in 1175208 from Python to JavaScript.
Javascript Code
function camelToSnakeCase(text) {
return text.replace(/(.)([A-Z][a-z]+)/, '$1_$2').replace(/([a-z0-9])([A-Z])/, '$1_$2').toLowerCase()
}
Working Examples:
camelToSnakeCase('thisISDifficult') -> this_is_difficult
camelToSnakeCase('thisISNT') -> this_isnt
camelToSnakeCase('somethingEasyLikeThis') -> something_easy_like_this

"alphaBetaGama".replace(/([A-Z])/g, "_$1").toLowerCase() // alpha_beta_gamma
Problem - Need to convert a camel-case string ( such as a property name ) into underscore style to meet interface requirements or for meta-programming.
Explanation
This line uses a feature of regular expressions where it can return a matched result ( first pair of () is $1, second is $2, etc ).
Each match in the string is converted to have an underscore ahead of it with _$1 string provided. At that point the string looks like alpha_Beta_Gamma.
To correct the capitalization, the entire string is converted toLowerCase().
Since toLowerCase is a fairly expensive operation, its best not to put it in the looping handler for each match-case, and run it once on the entire string.
After toLowerCase it the resulting string is alpha_beta_gamma ( in this example )

This will get you pretty far: https://github.com/domchristie/humps
You will probably have to use regex replace to replace the "." with an underscore.

I found this but I edited it so suit your question.
const camelToSnakeCase = str => str.replace(/[A-Z]/g, letter => `_${letter.toLowerCase()}`).replace(/^_/,'')

Good examples for js:
Snake Case
Kebab Case
Camel Case
Pascal Case
have here

function toCamelCase(s) {
// remove all characters that should not be in a variable name
// as well underscores an numbers from the beginning of the string
s = s.replace(/([^a-zA-Z0-9_\- ])|^[_0-9]+/g, "").trim().toLowerCase();
// uppercase letters preceeded by a hyphen or a space
s = s.replace(/([ -]+)([a-zA-Z0-9])/g, function(a,b,c) {
return c.toUpperCase();
});
// uppercase letters following numbers
s = s.replace(/([0-9]+)([a-zA-Z])/g, function(a,b,c) {
return b + c.toUpperCase();
});
return s;
}
Try this function, hope it helps.

"TestString".replace(/[A-Z]/g, val => "_" + val.toLowerCase()).replace(/^_/,"")
replaces all uppercase with an underscore and lowercase, then removes the leading underscore.

A Non-Regex Answer that converts PascalCase to snake_case
Note: I understand there are tons of good answers which solve this question elegantly. I was recently working on something similar to this where I chose not to use regex. So I felt to answer a non-regex solution to this.
const toSnakeCase = (str) => {
return str.slice(0,1).toLowerCase() + str.split('').slice(1).map((char) => {
if (char == char.toUpperCase()) return '_' + char.toLowerCase();
else return char;
}).join('');
}
Eg.
inputString = "ILoveJavascript" passed onto toSnakeCase()
would become "i_love_javascript"