How to Match Regex Instances Outside Quotes in JavaScript: A Comprehensive Guide

Matching Instances Not Enclosed in Quotes

In a previous question, it was suggested that matching all occurrences of a regex while excluding text within quotes is not feasible. However, this limitation can be overcome using a complex but effective regex.

The key to this regex is observing that a substring is outside of quotes if an even number of quotes precede it. This can be represented as the following look-ahead assertion:

(?=([^"]*"[^"]*")*[^"]*$)

This assertion ensures that the preceding text contains an even number of quotes followed by the current substring.

To exclude escaped quotes, we need to consider backslashes as well. The regex becomes slightly more complex:

\+(?=([^"\]*(\.|"([^"\]*\.)*[^"\]*"))*[^"]*$)

This regex first advances past any non-quote characters (S). Upon encountering a backslash or a quote, it either ignores the next character (if it is a backslash) or advances to the next non-escaped quote otherwise.

While this regex is somewhat intricate, it effectively matches all instances of the regex not enclosed within quotes, allowing for the desired result in JavaScript's split() and replace() methods.

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