# regexp/no-useless-lazy

disallow unnecessarily non-greedy quantifiers

  • ⚙️ This rule is included in "plugin:regexp/recommended".
  • 🔧 The --fix option on the command line (opens new window) can automatically fix some of the problems reported by this rule.

# 📖 Rule Details

This rule reports lazy quantifiers that don't need to by lazy.

There are two reasons why a lazy quantifier doesn't have to lazy:

  1. It's a constant quantifier (e.g. a{3}?).

  2. The quantifier is effectively possessive (e.g. a+?b).

    Whether a quantifier (let's call it q) is effectively possessive depends on the expression after it (let's call it e). q is effectively possessive if q cannot accept the character accepted by e and e cannot accept the characters accepted by q.

    In the example above, the character a and the character b do not overlap. Therefore the quantifier a+ is possessive.

    Since an effectively possessive quantifier cannot give up characters to the expression after it, it doesn't matter whether the quantifier greedy or lazy. However, greedy quantifiers should be preferred because they require less characters to write and are easier to visually parse.

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# 🔧 Options

Nothing.

# 🚀 Version

This rule was introduced in eslint-plugin-regexp v0.10.0

# 🔍 Implementation