Regex Practice 11/14

Greedy vs. lazy quantifiers

Phase 3's quantifiers (+, {n,m}) are all greedy by default - they grab as much text as possible while still letting the whole pattern match. Usually that's what you want, but it has a classic failure mode: pull the text between the first pair of quotes in 'Say "hello" and "goodbye"' and a greedy .+ doesn't stop at the first closing quote - it stops at the last one, because .+ between the outer quotes can still match, greedily, all the way to the end.

Add a ? right after the quantifier and it becomes lazy: it grabs as little as possible instead, stopping the moment the rest of the pattern is satisfied. .+? between two quotes stops at the very first closing quote. Same pattern shape, opposite instinct - and knowing which one you need is the difference between "it works" and "it somehow grabbed the whole file."

Your task: write extractGreedy(str), returning the text between the first " and the last " in str using a greedy quantifier, and extractLazy(str), returning the text between the first " and the next " using a lazy quantifier. Return null if str has no quoted text.

You'll practice:

Seeing greedy .+ overshoot to the last possible match
Making a quantifier lazy with .+? to stop at the first match instead

// Write extractGreedy(str): text between the first " and the LAST " (greedy).
function extractGreedy(str) {

}

// Write extractLazy(str): text between the first " and the NEXT " (lazy).
function extractLazy(str) {

}