Lexical structure
2.1 Character set
JavaScript is written in the Unicode character set and supports almost every language on the planet.
2.1.1 Uppercase and lowercase distinction
JavaScript is an uppercase and lowercase language.
2.1.2 Spaces, newlines and format control characters
JavaScript ignores spaces between tags, newlines, and the readability of code can be greatly improved by spaces and newlines. When spaces and newlines are required, Unicode escapes are used.
2.2 Gaze
single line gaze //here is a single line gaze
multi-line gaze /** multi-line gaze */
2.3 Direct quantity
A quantity that can be used directly in a program, such as a number. String, boolean, etc.
2.4 Identifiers and reserved words
identifier
Variable names must start with a letter (ab...), underscore (_), dollar ($), and non-starting parts can include alphanumeric, underscore, dollar, and other characters.
Javascript variables agree to appear in the Unicode complete set of characters as variable names. Such as: var π=3.14
reserved word
2.5 Optional semicolon
Assuming that the program statements are on each line, the semicolon can be omitted. The semicolon at the end of the program and {} can be omitted.