# regexp/no-optional-assertion
disallow optional assertions
- ⚙️ This rule is included in
"plugin:regexp/recommended".
# 📖 Rule Details
Assertions that are quantified (directly or indirectly) can be considered optional if the quantifier has a minimum of zero.
A simple example is the following pattern: /a(?:$)*b/. The $ assertion will reject but if that happens, it will simply be ignored because of the * quantifier. The assertion is optional, serving no function whatsoever.
More generally, an assertion is optional, if there exists a parent quantifier with a minimum of zero such that all possible paths of the quantified element that contain the assertion do not consume characters.
Here's an example: a(?:foo|(?<!-)(?:-|\b))*b. The \b is optional. However, the lookbehind (?<!-) is not optional because the group (?:-|\b) right after it can consume a character.
Optional assertions don't affect the pattern in any way. They are essentially dead code.
# 🔧 Options
Nothing.
# ❤️ Compatibility
This rule was taken from eslint-plugin-clean-regex (opens new window).
This rule is compatible with clean-regex/no-optional-assertion (opens new window) rule.
# 🚀 Version
This rule was introduced in eslint-plugin-regexp v0.9.0