JS Basics Review: Where JavaScript is written

Love to create Classroom JS Basic review: JavaScript writing position

Review

JS Writing Position:

The bottom of the body tag.

The actual work is written in a pair of script tags within the head tag.

Alert () Pop-up box.

Console.log ()

Literal:

Numeric literals: integers, floating-point numbers, special characters (Infinity,nan).

String literals: All languages, numbers in a language, special strings.

Variable:

Defining variables

Rules for identifiers: The first character is a letter (a-z,a-z), an underscore, a $. Other characters can be letters (A-Z,A-Z), underscores, $, numbers. (You cannot use the keyword specified in js, reserved words).

1 var A;

Variable assignment: The right value is assigned to the left.

1 A = 10;

Usually we write variable declarations and assignments together:

1 var a = 10;

Variable declaration elevation: Only the declaration is lifted, and the assignment of the variable is not promoted.

Data type: typeof ()

Number: Numeric type. integers, floating-point numbers, special characters.

String: Type.

The undefined:undefined type. Represents undefined. Oneself is a type.

Boolean: Boolean type. True,false.

Null: You are also a type.

The number type is converted to a string: number + "";

1 Console.log (12 + "3"); 123

The string type is converted to a number:

parseint (): Converted to an integer.

1 Console.log (parseint ("12.234 Hello World. 233")); 12

Parsefloat (): Converts a string to a floating-point number.

1 Console.log (parsefloat ("78.2341e3.7898 World")); 78234.1

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JS Basics Review: Where JavaScript is written