JavaScript Grammar Summary _ Basics

One: Grammar

JavaScript: A client-side scripting language based on object and event-driven;

Consists of the following three:

1,ecmascript (a ECMA International (formerly European Computer Manufacturers Association, European Computer Manufacturers Association, through ECMA-262 standardized scripting language);

2,bom (abbreviation of browser object model, referred to as the browser);

The 3,dom (Document Object model, the documentation objects models, referred to as DOM) is a standard programming interface recommended by the Consortium for processing extensible logo languages.

1 statement; execution order; annotation; introduction method; variable definition;

2) data type;

A:string, String type, enclosed in single double quotes for a string of characters (numbers, letters, symbols);

B:number, numeric type, integer value, floating-point number;

C:boolean, Boolean type, value is true/false;

d:undefined,undefined type, only Undefined a value, the default value for the variable;

E:null, only a special value of NULL, representing a null object pointer, you can set the variable to NULL to clear the variable;

F:object, object, reference type, also called complex type.

3) logical operators;

A: arithmetic operator: +,-,*,/,%;

B: relational operator: >,>=,<,<=,==,===,! =,!==;

C: Logical operators in:&& (with), | | (OR),! (non);

D: assignment operator: =,+=,-=,*=,/=,%=;

E: string and variable concatenation characters: "+";

F: Self-added (+ +), self-reduction (-);

4) type to replace;

String conversion Number: parseint ()---Converts other types to integers; parsefloat ()---Converts other types to floating-point (decimal);

5) Select structure;

Program three flow control: order, Branch (selection), loop;

1) If statement:

Single branch; double branch;

multiple branches; nested structure;

Note: the () after if () can not be omitted, {} in the branch cannot be omitted; If nesting does not exceed three layers

A: Single branch--if condition judgment statement;

B: multiple branches;

2) Swith statement;

Note: The default branch must be written in the Swith statement to prevent ambiguity in the maintenance of the following;

The probability of execution is greater than the front (if,case)

If else is different from the Swith, the former is branched with fewer nesting, the latter with more branches.

6 The conditional operator: The only three-wood operator, which requires three operands;

Format: expression 1? Expression 2: Expression 3;

First solution expression 1, if true, then execute expression 2, otherwise, execute expression 3;

7) circulation structure;

Loop: Repeated execution of a thing, given the conditions set up, repeated execution, know the condition does not establish failure to stop.

A:while cycle;

B:do while loop;

C:for cycle;

D:break and Countinue;

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