Question:

Explain what quantifiers are and describe at least 4 regular expression quantifiers.

Quantifiers are symbols that are used to target a range of matches. The best way to explain this is to just show you.

* Quantifier

The * star quantifier is used to match zero or more occurrences of a pattern.

For example :

var pattern /\bbo*\b/;  

Here I am saying match any word that begins with b and has zero or or more os. So b, bo, boo , booooooooooooooooooo would all be valid.

+ Quantifier

The plus quantifer has to have one match but can have as many afterwards.

For example :

var pattern = /\bboo+\b/; 

Here the pattern has to have at least boo but can have any of number of o’s afterwards so boooooooooo is valid.

? Quantifier

The question mark quantifer can only have one match or none.

var pattern = /(wonder)?\s+woman/;

Here we have a pattern that will match wonder woman with as many spaces between but there doesn’t have to be wonder as it will still match just woman.

{n} Quantifer

This quantifer allows us to specify the character or set it follows n times.

var pattern = /^(thunder\s){3}(cats){1}/ 

Here we we have a pattern that will match starting with the beginning of a string thunder thunder thunder cats with three thunder and one cat.