03-regular-expressions.md

How do I determine if a regex matches a string?

/regex/.test(string)

What regex operator do I use to search for multiple patterns?

Alternation or OR operator: |

 /yes|no|maybe/

How do I extract the actual matches of a pattern in a string?

"Hello, World!".match(/Hello/);

What is wildcard?

.

What is a negated character set?

[^abc]

What is a greedy match?

The longest possible part of a string that fits the regex pattern and returns it as a match

What is a lazy match?

The smallest possible part of the string that satisfies the regex pattern

What is the default matching strategy?

Greedy

How do I specify a lazy match?

/t[a-z]*?i/

What does \w match?

[A-Za-z0-9_]

What are shorthand character classes?

\w etc

How to I specify upper and lower number of patterns?

With quantity specifiers:

let multipleA = /a{3,5}h/;

How to I specify only a lower number of patterns?

let multipleA = /ha{3,}h/;

How to I specify exact number of patterns?

let multipleHA = /ha{3}h/;

What is a lookahead?

A pattern that tell JavaScript to look-ahead in your string to check for patterns further along

What is a positive lookahead?

A positive lookahead will look to make sure the element in the search pattern is there, but won't actually match it.

let quit = "qu";
let quRegex= /q(?=u)/;
quit.match(quRegex); // Returns ["q"]

What is a negative lookahead?

A negative lookahead will look to make sure the element in the search pattern is not there.

let noquit = "qt";
let qRegex = /q(?!u)/;
noquit.match(qRegex); // Returns ["q"]

How can you check two or more patterns in one string?

let password = "abc123";
let checkPass = /(?=\w{3,6})(?=\D*\d)/;
checkPass.test(password); // Returns true

How do we specify a pattern where the subpattern is repeated?

With capture groups:

let repeatStr = "regex regex";
let repeatRegex = /(\w+)\s\1/;
repeatRegex.test(repeatStr); // Returns true
repeatStr.match(repeatRegex); // Returns ["regex regex", "regex"]

How do I search and replace?

"Code Camp".replace(/(\w+)\s(\w+)/, '$2 $1');