const regex = /(.*?&.*?)&.*/;
const str = `https://www.bing.com/search?q=something+something+something+something&mkt=en-IN&organic=True&ads=False&snippet=False`;
const result = str.replace(regex, '$1');
The regular expression searches everything before the second “&” and replaces the original string with this match.
solved Regex for finding the second occurrence of a character in a dynamic string in javascript