Modern JavaScript Syntax and Practices CheatSheet
Variable & Expression
Basic Data Type
Regex
| 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. |
| 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 |
| 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
The reduce() method is used to apply a function to each element in the array to reduce the array to a single value.
Function
