JS advanced programming part3. object Basics

3.2Object Application

· Object abolition: if an object has two or more references, you must set all its references to null to abolish the object correctly.

Like java, JS has a garbage collection mechanism that automatically removes objects that are not referenced.

· Early binding and late binding

Binding: a method that combines object interfaces with instances.

Early binding: defines features and methods before instantiating an object;

Play binding: refers to in the compiler or interpretationProgramThe object type is unknown before running. Ecmascript uses late binding.

3.3Object Type

1. Local object

· Array class

The following example is used to describe its usage:

VaR arry = new array (10); // You can omit it if you do not know how big it is.CodeCan be added at will

VaR arry = new array ("red", "green", "blue ");

Alert (arry [1]); // "green"

VaR SCOR = "red, green, blue ";

VaR arry = SCOR. Split (","); // convert to array object

VaR SCOR = "green ";

VaR arry = SCOR. Split (""); // use an empty string to separate the string into the following characters: "g, R, E, E, N"

Array has two methods of string: Concat (): Connection/slice (): intercepting part of content

Array provides the stack function:

VaR stack = new array;

Stack. Push ("red ");

Stack. Push ("green ");

Alert (stack. tostring (); // "Red, Green"

VaR AA = stack. Pop (); // "green"

Shift (): the first entry of the array is deleted and returned as a function value. /Unshift.

Shift and push () can be used to complete the queue function.

· Date class

VaR d = new date (date. parse ("6/1/2011"); // If the passed string cannot be converted to a date, it will be Nan

VaR d = new date (date. UTC (2011,0, 6); // pay special attention to setting the month because the monthly setting starts from 0 (2011-1-6)

2. built-in objects

Ecmascript provides two built-in objects: Global and math;

Global eval () method: This method is like the whole ecmascript interpreter. It accepts a parameter, interprets it as a true ecmascript statement, and inserts it into the position of the function.

3. Host Object

All non-local objects are host objects, that is, objects in the host environment implemented by ecmascript. All BOM and DOM objects are host objects.

3.5Define a class or object

Use the constructor:

Function car (scolor, idoor ){

This. Color = scolor;

This. Doors = idoor;

This. showcolor = function (){

Alert (this. color)

};

}

VaR ocar = new car ('red', 4 );

VaR ocar2 = new car ("green", 3 );

Note: The object structure does not need to be defined and can be used directly in the constructor as needed.

The functions in the above created object are2Memory is wasted. (C ++,JavaThe functions of all objects in)

Improvement: put forward the function. After the constructor, add it with prototype. (The prototype attribute can be used to define the method)

Car. Prototype. showcolor = function () {alert (this. Color };

3.6Modify Object

Create a new method: Number. Prototype. tohexstring = function () {return this. tostring (16 )};

Re-define existing methods: If you re-define them, the existing methods will be overwritten, because ecmascript does not have to be overloaded.

 

More: http://blog.donews.com/me1105/archive/2011/02/10/118.aspx