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Summary of several common ways to create objects in js (recommended)_js object-oriented
Summary of several common ways to create objects in js (recommended)_js object-oriented
First mode: factory mode
var lev=function(){
return "Script Home";
};
function Parent(){
var Child = new Object();
Child. name="script";
Child.age="4";
Child.lev=lev;
return Child;
};
var x = Parent();
alert(x.name);
alert(x.lev());
Instructions:
1. Define the object in the function and define various properties of the object, Although the attribute can be a method, it is recommended to define the attribute whose attribute is a method outside the function, so as to avoid repeatedly creating the method
2. When referencing the object, use var x = Parent() instead var x = new Parent(); Because the latter may cause many problems (the former has also become a classic factory method, and the latter is called a hybrid factory method), it is not recommended to use the new method to use this object
3. In the function At the end, the object is returned
4. It is not recommended to create objects in this way, but you should understand
The second mode: constructor method
var lev=function(){
return "Script Home";
};
function Parent(){
this.name="script";
this.age="30";
this.lev=lev;
};
var x =new Parent();
alert(x.name);
alert(x.lev());
Explanation:
1. Compared with factory method, use constructor To create an object in a functional way, there is no need to recreate the object inside the function, but use this to refer to it, and the function does not need to explicitly return
2. Like the factory mode, although the value of the attribute can be a method, it is recommended to define the method in Outside functions
3.. Similarly, it is not recommended to create objects in this way, but you still need to understand
The third mode: Prototype mode
var lev=function(){
return "Script Home";
} ;
function Parent(){
};
Parent.prototype.name="Bruce Lee";
Parent.prototype.age="30";
Parent.prototype. lev=lev;
var x =new Parent();
alert(x.name);
alert(x.lev());
Description:
1. Do not define attributes in the function
2. Use the prototype attribute to define the attributes
3. Similarly, it is not recommended to create objects in this way
The fourth mode: mixed construction Function, prototype method (recommended)
function Parent (){
this.name="script";
this.age=4;
};
Parent.prototype.lev=function(){
return this.name;
};;
var x =new Parent();
alert(x.lev());
Explanation: 1. This pattern refers to mixing and matching constructors Method and prototype method
2. Define all attributes that are not methods in the function (constructor method)
Define all attributes whose values are methods outside the function using prototype (prototype method)
3. It is recommended to use this method to create objects. There are advantages to doing so and why not to use constructor method and prototype method separately. Due to space issues, we will not discuss it here
The fifth mode: dynamic prototype method
function Parent(){
this.name=" Script";
this.age=4;
if(typeof Parent._lev=="undefined"){
Parent.prototype.lev=function(){
return this.name;
}
Parent._lev=true;
}
};
var x =new Parent();
alert(x.lev( ));
Explanation:
1. The dynamic prototype method can be understood as a mixed constructor, a special case of the prototype method
2. In this mode, the attributes are methods The properties are defined directly in the function, but because
if (typeof Parent._lev=="undefined"){
Parent._lev=true;}
This ensures that when creating an instance of the object, the attribute method will not be repeated Create
3., it is recommended to use this mode
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