Regex for Code Refactoring — Find and Replace in Source Code

Code Refactoring with Regex

Regex find-and-replace is a powerful tool for batch code transformations that are too complex for simple text search but too simple to warrant writing a custom script.

Rename Variables with Word Boundaries

Find:    \boldName\b
Replace: newName

Word boundaries (\b) prevent matching substrings, so oldName in getOldName or oldNameValue will not be affected.

Convert camelCase to snake_case

Find:    ([a-z])([A-Z])
Replace: $1_$2

Then lowercase the result. Converts getUserName to get_user_name.

Update Function Signatures

Adding a parameter to all calls of a function:

Find:    fetchData\(([^)]+)\)
Replace: fetchData($1, { cache: true })

Convert console.log to Logger

Find:    console\.log\((.+?)\)
Replace: logger.info($1)

Update Import Paths

Find:    from ['"](\.\.?/components)/([^'"]+)['"]
Replace: from "@/components/$2"

Convert String Concatenation to Template Literals

You can search for string concatenation patterns using "([^"]*)" \\+ (\\w+) \\+ "([^"]*)" and convert them to template literal syntax.

Safety Tips for Code Refactoring

1. Always review changes before committing
2. Use version control — commit before large regex replacements
3. Test with a small scope first (single file)
4. Be cautious with greedy patterns in code that contains nested structures
5. Consider AST-based tools (jscodeshift, ts-morph) for complex refactoring