JavaScript object-oriented feature code examples_javascript skills

1. Use of basic classes
Method 1:

Copy code The code is as follows :

function sth(a) // Constructor
{
this.a = a;
this.fun = output; // Member function
}

function output(a, b, c)
{
document.write(this.a);
}

//Call
var s = new sth(250);
s.fun(1, 2, 3);
ouput(1, 2, 3); //If output is in sth It was wrong before

Method 2:

Copy code The code is as follows:

function sth(a)
{
this.a = a;
this.output = function()
{
document.write(this.a);
}
}

var s = new sth(2);
s.output(); // Output 2

2. Inheritance
Method 1:

Copy code The code is as follows:

function A(x)
{
this.x = x;
}

function B(x, y)
{
// Method 1
/*
this.construct = A;
this.construct(x);
delete this .construct;
*/

// Method 2
//A.call(this, x);

// Method 3
A.apply(this , new Array(x)); // You can also A.apply(this, arguments), but the order of arguments must be correct

this.y = y;
this.print = function()
{
document.write("x = ", x,
", y = ", y);
}
}

var b = new B(1, 2);
b.print();
alert(B instanceof A); // Output false

Advantages: Multiple inheritance can be achieved (just make multiple calls)

Disadvantages:
· Must be used as a constructor
· Using the instanceof operator to operate this type of inheritance results in false

Method 2:

Copy code The code is as follows:

function A()
{

}
A.prototype.x = 1;

function B()
{

}
B.prototype = new A(); // Cannot take parameters!
B.prototype.y = 2;
B.prototype.print = function()
{
document.write(this.x, ", ", this.y, "}

var b = new B();
b.print();
document.write(b instanceof A); // Output true

Disadvantages:
· Cannot implement multiple inheritance
· The constructor does not take parameters

Tips

Usually use mixed mode, both together

Copy code The code is as follows:

function A(x)
{
this.x = x;
}
A.prototype.printx = function() // Write into class A this.printx = function.... It’s also possible, the same below
{
document.write(this.x, "
");
}

function B(x, y)
{
A.call(this, x);
this.y = y;
}
B.prototype = new A(); // Cannot take parameters!
B.prototype.printxy = function()
{
document.write(this.x, ", ", this.y, "
");
}

var b = new B(1, 2);
b.printx(); // Output 1
b.printxy(); // Output 1, 2
document.write(b instanceof A); // Output true

3. Use of similar static member functions

Copy code The code is as follows:

function sth(a)
{
this.a = a;
}

sth.fun = function(s)
{
document.write(s.a );
}

var s = new sth(2);
sth.fun(s); // Output 2

4. Release of objects

Copy code The code is as follows:

var obj = new Object; // obj is a reference
obj = null; // Dereference will automatically perform garbage collection; if you need to release this object at all, assign all its references to null

5. Function object

Copy code The code is as follows:

var v = new Function("arg1", "arg2", "document.write(arg1 arg2);"); // Define a function object, the parameters are arg1, arg2
v(1, 2); // Will Will output 3

6. Callback function

Copy code The code is as follows:

function callback (func, arg)
{
func(arg);
}

function fun(arg)
{
document.write(arg);
}

//callback(func, "sb"); // This approach does not work

var func = new Function("arg", "fun(arg);");
// Of course, you can also replace func(arg) with specific execution code,
// But it is best to do this if the function code is huge
callback(func, "sb");

7. Overloading of functions

Copy code The code is as follows:

function fun()
{
switch (arguments.length)
{
case 1:
document.write(arguments[0]);
break;
case 2 :
document.write(arguments[0] arguments[1]);
break;
default:
document.write("ERROR!");
break;
}
}

fun(1);
fun(1, 2);

8. Use function closures to implement functions with "static variables"

Copy code Code As follows:

function fun()
{
var v = 1;
function fun2()
{
v;
document.write(v);
document.write("
");
return v;
}

return fun2;
}

var func = fun() ;
func(); // Output 2
func(); // Output 3
func(); // Output 4