JavaScript mode (2)--Singleton mode

Single-chat mode is a very extreme pattern that guarantees that a class has only one entity in the entire application domain, which means that when you create instances of a class multiple times, they are the first ones created.

In a Java or C # environment, it is simple to implement a singleton pattern, just define a static variable, save the object in a static variable, and the static variable does not change with the class instance. Similarly, JavaScript is a similar implementation principle.

Common static variables for single-instance mode

var Earth = (function  () {    if (typeof earth.instance = = = ' object ') {         C8>return  earth.instance;    }     this. Name = "Earth";     this. Age = $ * * + * 10000;      This ;     return earth.instance;});

The earth.instance in the code is a public static variable, and the public static variable is invisible in the instantiated object earth1

But it can be seen in the Earth class.

var New Earth (); var New  = = = Earth2);

Because it is a singleton mode, the result is obviously ' true '

Private static variables for single-instance mode

Storing an instance in a public variable is simple, but there is a fatal problem that the public variable can be changed externally, so the best way to use private static variables is to use a private static variable that needs to be implemented by a timely function and a closure.

varEarth = (function () {      varinstance; return function () {            if(typeofInstance = = = ' object ') {            returninstance; }         This. Name = "Earth";  This. Age = 46 * 1000 * 1000 * 10000; Instance= This; returninstance; }}());

The entire function returns a closure function and executes immediately, in a timely manner: (function () {} ())

Execute again

var New Earth (); var New  = = = Earth2);

The results are still ' true '

Summarize:

Singleton mode is very extreme mode, can be implemented by static variable storage instances, through the implementation of private static need to rely on timely functions and closures, on-time functions and closures are no longer cumbersome here.

JavaScript mode (2)--Singleton mode