2nd Chapter Lexical Structure

1. JavaScript programs are written in the Unicode character set. So the variable name can be Chinese.

2. JavaScript is a case-sensitive programming language. But HTML is not case-sensitive. Because HTML and client-side JavaScript are closely linked, this is easily confusing.

For example, when you set an event handler in HTML, the OnClick property can be written as an onclick, but you must use the lowercase onclick in JavaScript.

3. JavaScript ignores the spaces between tokens in the program and, in most cases, ignores line breaks. Because you can freely use spaces and line breaks in your code, you can adopt a neat, consistent indentation of the unified coding style.

4. For Unicode characters that cannot be displayed with the keyboard, JavaScript defines a Unicode escape sequence to represent Unicode characters: \uxxxx.

5. JavaScript is annotated in the same way as C, \ \ or/**/.

6. JavaScript identifiers are used to name variables or functions, starting with letters, underscores (_), or dollar ($) characters, followed by letters, numbers, underscores, or dollar symbols. Although JS allows any character in the Unicode character set to be used in an identifier, it is usually used only in ASCII letters for portability and easy writing purposes.

7. A semicolon that separates different statements in JavaScript is optional.

2nd Chapter Lexical Structure