JavaScript Basics (objects, functions, and objects)

- , Objects

Properties: Describes an object's information method: Describes the behavior of an object encapsulation: only care about input and output (regardless of how the process is implemented)

ü Categories of objects:

Built-in objects (native objects): Are predefined objects in the JavaScript language (such as String/number).

Host objects: Generally implemented by the browser environment, mainly divided into BOM and DOM.

Custom objects: Objects that are created autonomously by developers.

ü Creation of the object:

• ? initializer mode

var Object Name = {

Property name : Property value ,

Method name : function () { method body } ---[equivalent to the right half of the literal definition function ]

}

• constructor function mode

( 1 ) var Object Name       = new Object (); --- new-keyword, which means to create an object

Object Name . Property name = Property Value         ; ---Object-is an ancestor of objects in JavaScript

Object Name . Method Name = function () {};

( 2 ) Custom Constructors

• Object.create () method

(1) An object must exist in advance Hero1

Eg:var Hero2 = object.create (hero1); The new object created by---has the same properties and methods as the object being passed

(1) Create an empty object

Eg: var object name = object.create (null); Hero4.name = ' zhaomin ';

U Use Object

Method One method two

Console.log ( object name . Property name ); console.log ( object name [' property name ']);

Object Name . Method Name (); object name [' method name '] () ;

[Note: Not applicable to complex naming methods] [Note: For complex naming methods] [More general usage]

Eg:content-type:number---writing errors

'content-type': number; Console.log (Hero.content-type); ---output error

The "-" is resolved to the subtraction operator;  Hero.content-Property acquisition failed; Type-not a variable

Console.log (hero[' content-type '); ---correct

Attached: Window object

* is an object in the BOM that represents the window of the current browser; is also the top-level object in the browser environment (global object)

* Defined global variables and global functions, properties and methods added for Window objects

Eg:var name = ' Zhao min ';

var sayme = function () {

Console.log (' My name is Zhaomin ');

}

Console.log (Window.name);

Window.sayme ();

Properties and methods of the U-action object

2 new objects

Object Name . the new property name = Property Value         ; the name of the object . the new method name = function () {};

2 modifying objects

Object Name . Original Property name = the new property value     ; the name of the object . Original Method Name = function () {};

2 deleting objects

Delete Object Name . Property name Delete Object Name . Method Name

U traversal (enum) object

Only the object name is known, but the property and method name typeof or instanceof are unclear;

• For...in Cycle:

This method accesses all the enumerable properties of an object and its prototype chain in turn.

Format: for (var A in object name) {A---Represents the object's property name and method name

if (typeof hero[a] = = ' function ') {Distinguishing properties and methods-typeof operator

Hero[a] (); ---must be the method of the object

} else {

Console.log (Hero[a]); ---must be an object's property

}

Result: Gets all the properties or method names of the specified object

• Object.keys (obj) method:

The obj---represents the traversal of the current object return value: An array containing all the property names and method names of the current object eg:var a = Object.keys (Hero);   Console.log (a); ["Name", "Age", "Sayme"]

• Object.getownpropertynames (Object) method:

This method is the same as above.

U detects the properties or methods of an object (that is, whether the specified attribute exists in the detection object:)

* Use the IN keyword console.log (' name ' in FN);

Use the hasOwnProperty () method Console.log (Fn.hasownproperty (' name ') for object objects);

Use undefined to judge console.log (fn.name = = = undefined);

Use the IF statement to determine. if (fn.name) {

Console.log (' name attribute exists ');

}

Note: The call object does not exist for the property---undefined

A method that calls an object that does not exist---output error is a function

- , functions, and objects

JavaScript Basics (objects, functions, and objects)