Modern JavaScript Syntax and Practices CheatSheet

Variable & Expression

Basic Data Type

Regex

• Symbols

Term	Description
.	(period) Matches any single character, except for line breaks.
*	Matches the preceding expression 0 or more times.
+	Matches the preceding expression 1 or more times.
?	Preceding expression is optional (Matches 0 or 1 times).
^	Matches the beginning of the string.
$	Matches the end of the string.

• Character groups

Term	Description
\d	Matches any single digit character.
\w	Matches any word character (alphanumeric & underscore).
[XYZ]	Character Set: Matches any single character from the character within the brackets. You can also do a range such as [A-Z]
[XYZ]+	Matches one or more of any of the characters in the set.
[^a-z]	Inside a character set, the ^ is used for negation. In this example, match anything that is NOT an uppercase letter.

• Flags: There are five optional flags. They can be used separately or together and are placed after the closing slash. Example: /[A-Z]/g I’ll only be introducing 2 here.

Term	Description
g	Global search
i	case insensitive search

• Advanced

Term	Description
(x)	Capturing Parenthesis: Matches x and remembers it so we can use it later.
(?:x)	Non-capturing Parenthesis: Matches x and does not remembers it.
x(?=y)	Lookahead: Matches x only if it is followed by y.

Collection

Array

Transform

The reduce() method is used to apply a function to each element in the array to reduce the array to a single value.

Function