Understanding Regex Capture Groups and Backreferences
Capture groups enclosed in parentheses (e.g., (\d{4})-(\d{2})-(\d{2})) isolate reusable substrings from matching filenames.
Numbered replacement tokens ($1, $2 in JavaScript/VS Code or \1, \2 in POSIX tools) allow you to reorder, prepend, or append text components dynamically.
Zero-Leak Client-Side Pattern Testing
Testing batch expressions against production files can risk accidental overwrites. Using DocSwift's local regex tools allows you to preview matches and substitutions in browser RAM without affecting disk storage.
Step-by-Step Tutorial
Analyze Filename Variations
Examine common structures across your file list, such as raw camera dumps (IMG_20261107_WA0001.jpg).
Formulate Match Capture Groups
Build an anchored pattern: ^IMG_(\d{4})(\d{2})(\d{2})_WA(\d{4})\.jpg$ to segment year, month, day, and serial index.
Define Reordered Substitution Syntax
Design target format: $1-$2-$3_Photo-$4.jpg to produce clean, ISO-standard, chronologically sortable filenames.
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Frequently Asked Questions
What is the difference between $1 and \1 in regex replacement?
Modern JavaScript, editors, and web tools use $1 for group backreferences, whereas Python re.sub and vim traditionally use \1.
Can regex change file extensions safely?
Yes, by capturing (.*)\.jpeg$ and substituting $1.jpg, you can normalize extensions in bulk.