Regex - Basic information

regex.md

Reference

Meta Sequences:

• . (a dot) It denotes “any character except a newline”

Quantifiers:

• + to the match one character after another.
• ? is a quantifier by itself (zero or one), but if added after another quantifier (or even itself) it gets another meaning – it switches the matching mode from greedy --> to --> lazy.

Quantifiers

Greedy search

let regex = /".+"/g
let str = `a "witch" and her "broom" is one...`

str.match(regex) 
// "witch" and her "broom"

Lazy mode

It means: “repeat minimal number of times”.

let regex = /".+?"/g
let regexAlternativeApproach = /"[^"]+"/g;
let str = `a "witch" and her "broom" is one...`

str.match(regex) 
// "witch"
// "broom"

Inspirations

• javascript.info - Greedy and lazy quantifiers

g guarda um state de lastIndex. Não é exatamente regex, mas a implementação do js. Se tem o ^ e $ tem pouco motivo pra usar /g. - https://stackoverflow.com/questions/1520800/why-does-a-regexp-with-global-flag-give-wrong-results

https://lemire.me/blog/2021/04/22/some-useful-regular-expressions-for-programmers/