Regular Expressions in Javascript

An overview of regular expressions in Javascript. Intended as a supplement to Eloquent Javascript ch.9 by Marijn Haverbeke.

Transcript

1. Eloquent JS Chapter 9 Regular Expressions
2. Literal notation /ab+c/i;
3. Constructor new RegExp('ab+c', 'i'); new RegExp(/ab+c/, 'i'); Don't forget the normal string escape rules for special characters!
4. Test /abc/.test("abcde"); => true /abc/.test("defgh"); => false
5. Exec /abc/.exec("abcde"); => ["abc"] /abc/.exec("defgh"); => null
6. An object with information about the match /abc/.exec("defabcde").index; => 3 /abcff/.exec("defabcde").index; => null
7. Search "abc0def".search(/\d/); => 3 "abcdef".search(/\d/); => -1
8. Replace "papa".replace("p", "m"); => "mapa"
9. Replace "adage".replace(/[ae]/, "u"); => "udage" "adage".replace(/[ae]/g, "u"); => "udugu"
10. Flags (aka modifiers) i - Perform case-insensitive matching g - Perform a global match m - Multiline
11. Brackets [abc] - Matches any single character a, b, or c [^abc] - Matches any character except a, b, c [a-c] - Matches any character from a to c
12. Brackets (ab|cd) - Matches ab or cd (...) - Captures anything enclosed
13. Character Classes . - Any character except newline \d - Any digit \D - Any non-digit
14. Character Classes \w - Alphanumeric (word) character \W - Non-alphanumeric character \s - Whitespace character \S - Non-whitespace character
15. No love for non-Latin characters "éβ".search(/\w/); => -1 Try xRegExp or defining word characters using Unicode.
16. Boundaries ^ - Start of line $ - End of line \b - At beginning or end of word \B - Not at beginning or end of word
17. Quantifiers n+ - Match one or more n n* - Match zero or more n's n? - Match zero or one n's
18. Quantifiers n{3} - Match sequence of 3 n's n{3,5} - Match sequence of 3 to 5 n's n{3,} - Match sequence of 3 or more n's
19. Assertions x(?=y) - Matches x only if x is followed by y x(?!y) - Matches x only if x is not followed by y
20. Capture Groups "Hopper, Grace\nLovelace, Ada".replace(/([\w ]+), ([\w ]+)/g, "$2 $1"); => "Grace Hopper Ada Lovelace"
21. Greedy Operators + * ? {} /<.+>/.exec("<p>Hello world</p>"); => "<p>Hello world</p>" /<.+?>/.exec("<p>Hello world</p>"); => "<p>"
22. Help! scriptular.com MDN | Regular Expressions regexr.com