JavaScript Syntax Summary

One: Grammar

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

Consists of the following three:

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

2,bom (abbreviation for browser object model, referred to as a browser-based);

The 3,dom (Document Object model, the documentation-based, or DOM) is the standard programming interface recommended by the Organization for the processing of extensible flag languages.

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

2) data type;

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

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, there is only one special value null, which represents an empty object pointer, which can be set 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 operator in:&& (with), | | (OR),! (non);

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

E: string and variable concatenation: "+";

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

4) type loading and replacement;

String conversion numbers: parseint ()---Convert other types to integers, parsefloat ()---Convert other types to floating-point (decimals);

5) Select the structure;

Program three flow control: order, Branch (select), cycle;

1) If statement:

Single branch; double branch;

multiple branches; nested structures;

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

A: Single branch--if conditional judgment statement;

B: Multi-branch;

　　

2) Swith statement;

　　　

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

Put more execution probabilities in front (if,case)

If else and swith differ, the former is branched with less nesting and the latter with more branches.

6) Condition Operator: The only three-wood operator, which requires three operands;

Format: expression 1? Expression 2: Expression 3;

The expression 1 is first, if true, the expression 2 is executed, whereas the expression 3 is executed;

7) cyclic structure;

Loop: Repeat one thing, given the conditions set up, repeated execution, know that the condition is not established failure stop.

A:while cycle;

B:do while loop;

C:for cycle;

D:break and Countinue;

JavaScript Syntax Summary