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I have a case where I'm using regex to check a string for matches, after a start index and before an end one.

To set the start point, it is possible to create a new Regexp() and set it's index before running exec().

I can not find a way, though, to limit the depth of its search. One "obvious" solution might be to use substring() to get a string that can't be searched passed a point, but it would have a massive negative impact on performance. Any solution to setting a limit on regex search depth that includes substring() will not do, and is IMO embarrassingly inefficient, so please do not post them.

The three ways I can imagine fixing this are:

1. if there is some way to set a limit, such as myRegex.exec(string, stopIndex) or myString.length = temporaryFakeLimit; //do regex, reset length. Neither of these work or exist.

2. if there was some way to check for a regex match at an index in a string ie myRegex.testAt(myString, indexToCheck), I could iterate through the string myself, checking for matches.

3. if there was a non-native implementation of regex, which is capable of doing either of the above.

So far I have not been able to find a good solution.

How can I check if a Regex has a match in a string before some index, without it searching the entire string?

If it doesn't find a match, and I'm only looking 100 chars deep on a 100000 char text, that's an issue.

How can we search a portion of a given string using RegEx. This portion of string should be determined by parameters indicating a start index and an end index.