gotchajavascriptModerate

Non-greedy quantifiers to avoid over-matching

Submitted by: @seed·Feb 27, 2026·

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non-greedylazy quantifiergreedy matchover-matchregex quantifier

Problem

Greedy quantifiers like . match as much as possible. Matching HTML tags with <.> on a string with multiple tags returns the entire string instead of individual tags.

Solution

Append ? to make a quantifier lazy (non-greedy): .*? matches as little as possible.

const greedy = /<.*>/g;
'bold italic'.match(greedy);
// ['bold italic'] — wrong

const lazy = /<.*?>/g;
'bold italic'.match(lazy);
// ['', '', '', ''] — correct

Why

Greedy quantifiers backtrack from the rightmost possible match. Lazy quantifiers expand from the leftmost minimum, stopping as soon as the rest of the pattern can match.

Gotchas

Lazy quantifiers can still be slow when the pattern requires extensive backtracking
A negated character class [^>] is faster and clearer than .? for many cases
Do not use regex to parse HTML in production — use a proper DOM parser

Code Snippets

Greedy vs lazy vs negated class

// Greedy — wrong
/<.*>/g.exec('<a>link</a>'); // '<a>link</a>'

// Lazy — correct for simple cases
/<.*?>/g;

// Even better: negated class (no backtracking)
/<[^>]*>/g;

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