Regular Expressions

Regular expressions, often shortened to "regex" or "regexp", are patterns that help programmers match, search, and replace text. Regular expressions are powerful, but can be difficult to understand because they use so many special characters.

Your first regular expression will be used to catch help requests. Declare a helpRegex variable, and assign it a regular expression that matches the string please help.

As a refresher, here is a regular expression to match the string hello world:

Example Code
const regex = /hello world/;

Regular expressions can take flags to modify their behavior. For instance, the i flag can be used to make the expression ignore case, causing it to match hello, HELLO, and Hello for the expression /hello/.

Flags are added after the trailing slash. 

Strings have a .match() method, which accepts a regular expression as an argument and determines if the string matches that expression.

Instead of using the .match() method, you can use the .test() method of a regular expression to test if a string matches the pattern. Unlike .match(), .test() returns a boolean value indicating whether or not the string matches the pattern.

The alternate sequence | can be used to match either the text on the left or the text on the right of the |. For example, the regular expression /yes|no/ will match either yes or no.

A character class is defined by square brackets, and matches any character within the brackets. For example, [aeiou] matches any character in the list aeiou. You can also define a range of characters to match using a hyphen. For example, [a-z] matches any character from a to z.

The value may be more than one digit. To match this, the + quantifier can be used - this matches one or more consecutive occurrences. For example, the regular expression /a+/ matches one or more consecutive a characters.

A capture group is a way to define a part of the expression that should be captured and saved for later reference. You can define a capture group by wrapping a part of your expression in parentheses. For example, /h(i|ey) camper/ would match either hi camper or hey camper, and would capture i or ey in a group.

Now that you have your capture group, you can mark the entire pattern as an optional match. The ? quantifier matches zero or one occurrence of the preceding character or group. For example, the regular expression /colou?r/ matches both color and colour, because the u is optional.

One last thing with this expression. You don't actually need the match value from your capture group, so you can turn it into a non-capturing group. This will allow you to group the characters together without preserving the result.

To create a non-capturing group in a regular expression, you can add ?: after the opening parenthesis of a group. For instance, (?:a|b) will match either a or b, but it will not capture the result.

Your regex should match whole words, not partial words. That is, you do not want to match hands-free money management.

To do this, start by checking for spaces before and after your pattern. You can do this by using the meta character \s, which will match spaces, tabs, and line breaks.

Like the ^ anchor, you can use the $ anchor to match the end of the string.