Learn JavaScript II from scratch (basic concept)

Basic concept One, case-sensitive

Everything in ECMAScript (variables, function names, operators) is case-sensitive.

The variable name test and test represent two different variables, respectively.

Second, identifiers

The so-called identifier refers to the name of a variable, function, property, or parameter of a function. One or more characters that are combined by identifiers according to the following formatting rules:

• The first character must be a letter, an underscore (_), or a dollar sign ($);
• Other characters can be letters, underscores, dollar signs, or numbers.
• The ECMAScript identifier is in hump case format, that is, the first letter lowercase, and the first letter of each of the remaining words is capitalized, for example: Firstsecond,mycar,dosomethingimport

Third, comments

ECMAScript uses C-style annotations, including single-line comments and block-level annotations.

• Single-line comment: Start with two slashes such as:

// single-line comment

• Block-level comments begin with a slash and an asterisk (/*), ending with an asterisk and a slash (*/) such as:

/* * This is a multi-line * (Block-level) Comment */

Iv. statements

The statement in ECMAScript ends with a semicolon, and if you omit the semicolon, the parser determines the end of the statement, such as:

var sum = a + b   // Even if no semicolon is a valid statement-------does not recommend var diff =-A;  // recommended---------Valid statements

Although the ending semicolon is not required, it is recommended that you do not omit it at any time.

V. Keywords and reserved words

Keywords and reserved words: characters that have a specific purpose, which can be used to denote the start or end of a control statement, or to perform a specific operation.

Keywords and reserved words: cannot be an identifier or a property name.

Learn JavaScript II from scratch (basic concept)