I have a string like this:
124:111,120:444,103:504,494:120,404:111,200:100,

I will use replace() and let’s say I want to select
124:111,120:444,103:504,494:120,404:111,**200:100,**
without actually defining 200:100, but instead having it to work like this:

Define only :100, regex selects everything to the left until "," approaches and everything to the right including first "," => 200:100,

Is it possible to have such a regex? Thanks for any information

>Solution :

Regex

,?(\d*?):100

Will match :100 and capture the digits before that:

const regex = /,?(\d*?):100/gm;
const sourceValue = '124:111,120:444,103:504,494:120,404:111,200:100,';
const match = regex.exec(sourceValue);

console.log(match[1]);
// 200

split()

Another option is to split on ,, then check if the right side has the value you’re searching for

const sourceValue = '124:111,120:444,103:504,494:120,404:111,200:100,';
const searchValue = 100;

sourceValue.split(',').forEach(p => {
    const [ l, r ] = p.split(':');
    if (+r === searchValue) {
        console.log(`Found searchValue\n\nLeft\t\t${l}\nRight\t\t${r}\nOriginal\t${p}`);
    }
});