How to Use Alternation Inside Square Brackets in Regular Expressions (Regex)?

Understanding the Issue with Alternation Inside Square Brackets

While creating a regular expression (regex) for a search engine string, you encountered a challenge with alternation within square brackets. Your regex aimed to match strings with 'wd' in addition to 'word' or 'qw'. Despite experimenting with different approaches, you were unable to achieve the desired result.

Simply enclosing multiple characters within square brackets does not perform alternation in JavaScript; it instead denotes a character set. Alternation, which matches multiple alternatives within a specific order, is accomplished using parentheses. Therefore, the correct syntax should be:

.*baidu.com.*[/?].*(wd|word|qw){1}=

or

.*baidu.com.*[/?].*(?:wd|word|qw){1}=

By enclosing the alternatives ('wd', 'word', and 'qw') within parentheses, you enable alternation. The '?:' before the parentheses in the second regex makes the grouping non-capturing, which prevents it from being assigned a capturing group ID during matching.

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