javascript - JavaScript中的静态变量(Static variables in JavaScript)

Question

如何在Javascript中创建静态变量？

  ask by Rajat translate from so

Answer 1

If you come from a class-based, statically typed object-oriented language (like Java, C++ or C#) I assume that you are trying to create a variable or method associated to a "type" but not to an instance.

(如果你来自基于类的，静态类型的面向对象语言（如Java，C ++或C＃），我假设您正在尝试创建与“类型”相关但不与实例相关联的变量或方法。)

An example using a "classical" approach, with constructor functions maybe could help you to catch the concepts of basic OO JavaScript:

(使用“经典”方法的示例，使用构造函数可能可以帮助您捕获基本OO JavaScript的概念：)

function MyClass () { // constructor function
  var privateVariable = "foo";  // Private variable 

  this.publicVariable = "bar";  // Public variable 

  this.privilegedMethod = function () {  // Public Method
    alert(privateVariable);
  };
}

// Instance method will be available to all instances but only load once in memory 
MyClass.prototype.publicMethod = function () {    
  alert(this.publicVariable);
};

// Static variable shared by all instances
MyClass.staticProperty = "baz";

var myInstance = new MyClass();

staticProperty is defined in the MyClass object (which is a function) and has nothing to do with its created instances, JavaScript treats functions as first-class objects , so being an object, you can assign properties to a function.

(staticProperty在MyClass对象（它是一个函数）中定义，与其创建的实例无关，JavaScript将函数视为第一类对象 ，因此作为对象，您可以为函数指定属性。)