Starting with v8.8, V8 ships with a new experimental non-backtracking RegExp engine (in addition to the existing Irregexp engine) which guarantees execution in linear time with respect to the size of the subject string. The experimental engine is available behind the feature flags mentioned below.
In its default configuration, V8 compiles regular expressions to native code upon the first execution. As part of our work on JIT-less V8, we introduced an interpreter for regular expressions. Interpreting regular expressions has the advantage of using less memory, but it comes with a performance penalty. In this blog post we describe how we take advantage of the upsides of interpreting regular expressions while mitigating the downsides.
This blog post covers V8’s recent migration of RegExp’s built-in functions from a self-hosted JavaScript implementation to one that hooks straight into our new code generation architecture based on TurboFan.
Introduced with the third edition of the ECMA-262 specification, regular expressions have been part of Javascript since 1999. In functionality and expressiveness, JavaScript’s implementation of regular expressions roughly mirrors that of other programming languages.