CODEWITHSUNDEEP
javascriptregex
Vincent Scheib
Vincent Scheib

Reputation: 18650

How to match a substring surrounded by known prefix and suffix in javascript

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?

Upvotes: 8

Views: 16569

Answers (2)

zer00ne
zer00ne

Reputation: 44086

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]);

Upvotes: 1

Vincent Scheib
Vincent Scheib

Reputation: 18650

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.

Upvotes: 14

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