RegExp compile()
RegExp.prototype.compile() is a legacy method for reconfiguring an existing regular expression object. Modern JavaScript creates a new RegExp instead of mutating one in place.
Overview
RegExp.prototype.compile() is a legacy method for reconfiguring an existing regular expression object. Modern JavaScript creates a new RegExp instead of mutating one in place.
Browser support
| Feature | Desktop | Mobile | ||||
|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Safari | Chrome Android | Safari iOS | |
javascript.builtins.RegExp.compile Deprecated | 1 | 12 | 1 | 3.1 | 18 | 2 |
1+Supported (version) Not supported ※Has note Sub-feature descriptions sourced from MDN Web Docs (CC BY-SA 2.5)
Syntax
JAVASCRIPT
// RegExp compile() example
// See MDN Web Docs for detailsLive demo
Reuse one RegExp object
Call compile when available to replace the pattern on the same instance.
JavaScript
Output
Press the Run button
Switch between patterns
Retarget a single RegExp instance to check multiple formats.
JavaScript
Output
Press the Run button
Compare with new RegExp
Show the modern alternative to compile by constructing a new RegExp.
JavaScript
Output
Press the Run button
Use cases
Regex modernization
Replace compile()-based flows with clearer new RegExp(...) creation during refactors.
Legacy code reading
Recognize what compile is doing when auditing historical regular-expression utilities.
Cautions
- Mutating regex objects makes pattern flow harder to follow than building a fresh value.
- Deprecated APIs increase maintenance cost and rarely justify their continued use.
Accessibility
- No direct accessibility effect, but clearer validation code supports more reliable user feedback.
- Prefer maintainable regex handling in forms and parsing paths that drive visible errors.
Related links
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