Given a string, such as:

example string with an intended nested string to match.

How to isolate a substring knowing only a prefix and suffix for it, e.g. between intended and to match?

Given a string, such as:

example string with an intended nested string to match.

How to isolate a substring knowing only a prefix and suffix for it, e.g. between intended and to match?

• javascript
• regex

2 Answers 2

Use regular expressions with non-capturing parentheses, like so:

string = 'example string with an intended nested string to match.';
regexp = /(?:intended)(.*)(?:to match)/;
firstMatch = regexp.exec(string)[1]; // " nested string "

The question mark has several uses in regular expressions, the parentheses question mark colon form (?:more regex) is the non-capturing parentheses.

See MDN for more details of exec(), string.match(), and regular expressions.

Look behind (?<=...) and look ahead (?=...) can be used to the same effect -- they are used to match but are not included in the result, the term for that behavior is referred to as "not consuming"

RegExp Lookahead Lookbehind

/(?<=intended).+(?=to match)/g;

RegEx101

const str = `example string with an intended nested string to match.`;

const rgx = /(?<=intended).+(?=to match)/g;

const hit = str.match(rgx);

console.log(hit[0]);