How to Match Regex Instances Outside of Quoted Strings, Even with Escaped Quotes?

Matching Instances Outside of Quotes

Contrary to previous assumptions, it is possible to match all instances of a given regex that are not within quoted portions of a string using regular expressions, even accounting for escaped quotes.

Regex Solution

To achieve this, utilize a look-ahead assertion that checks if each word is outside of quotes, which occurs when there are an even number of quotes following it. The regex below captures this pattern:

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

Dealing with Escaped Quotes

To handle escaped quotes, modify the expression to ignore backslashes and advance to the next unescaped quote:

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

This ensures that escaped quotes are not counted as opening quotes.

JavaScript Usage with .split() and .replace()

For use with JavaScript's .split() and .replace() methods, the following code can be employed:

const input = '+bar+baz"not+or\"+or+\"this+\"foo+bar+';
const replaced = input.replace(/\+(?=([^"\]*(\.|"([^"\]*\.)*[^"\]*"))*[^"]*$)/g, '#');
console.log(replaced); // "#bar#baz\"not+or\"+or+\"this+\"foo#bar#"

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