Regex Quantifiers

Quantifiers

Quantifiers specify how many times a pattern must match. They apply to the preceding character, group, or class.

Example

/a*/     // 0 or more "a"
/a+/     // 1 or more "a"
/a?/     // 0 or 1 "a" (optional)
/a{3}/   // exactly 3 "a"
/a{2,4}/ // 2 to 4 "a"
/a{2,}/  // 2 or more "a"

// Greedy vs lazy
/".+"/   // Greedy: matches as much as possible
/".+?"/  // Lazy: matches as little as possible

"say \"hi\" and \"bye\"".match(/".+"/g);  // ["\"hi\" and \"bye\""] greedy
"say \"hi\" and \"bye\"".match(/".+?"/g); // ["\"hi\"", "\"bye\""] lazy

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Pro Tip

Add ? after a quantifier (+?, *?, {n,m}?) to make it lazy — it stops at the first valid match instead of the last.

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