类方法如何在 javascript 中实现

How the class methods are implemented in javascript?

本文关键字：实现 javascript 类方法      更新时间：2023-09-26

我正在学习一个库，看到一个例子，我不明白它是怎么做到的？在类的函数中，"this"变量包含类的所有方法。在外面，只有公共方法可用。

受保护的方法更有趣。它们仅在继承的类中可用。它是如何工作的？

请参阅以下文档中的示例：

/**
  * A-class
  */
var ClassA = AWeb.class({
   public : {
      /**
        * A-class constructor
        */
      constructor : function() {
         /* Private variable */
         this.variable1 = "A";
         this.calls = 0;
      },
      /**
        * Function returns information about the object
        */
      getInfo : function() {
         this.incCalls();
         return "variable1=" + this.variable1 + ", calls=" + this.calls;
      }
   },
   protected : {
      /**
        * Protected function
        */
      changeVariable1 : function( value ) {
         this.variable1 = value;
      }
   },
   private : {
      /**
        * Private function
        */
      incCalls : function() {
         this.calls++;
      }
   }
});
/**
  * C-class
  */
var ClassC = AWeb.class({
   extends : ClassA,
   public : {
      /**
        * B-class constructor
        */
      constructor : function() {
         this.super();
         this.changeVariable1( "C" );
      },
      /**
        * Function returns extended information about the object
        */
      getLongInfo : function() {
         return this.incCalls !== undefined ? "incCalls visible" : "incCalls undefined";
      }
   }
});
/**
  * Main project function
  */
function main() {
   var a = new ClassA(),
       c = new ClassC();
   alert(
      "a instanceof ClassA: " + (a instanceof ClassA) + "'n" +
      "a instanceof ClassC: " + (a instanceof ClassC) + "'n" +
      "a.getInfo " + (a.getInfo ? "exists" : "undefined") + "'n" +
      "a.getLongInfo " + (a.getLongInfo ? "exists" : "undefined") + "'n" +
      "a.changeVariable1 " + (a.changeVariable1 ? "exists" : "undefined") + "'n" +
      "a.getInfo()=" + a.getInfo() + "'n'n" +
      "c instanceof ClassA: " + (c instanceof ClassA) + "'n" +
      "c instanceof ClassC: " + (c instanceof ClassC) + "'n" +
      "c.getInfo " + (c.getInfo ? "exists" : "undefined") + "'n" +
      "c.getLongInfo " + (c.getLongInfo ? "exists" : "undefined") + "'n" +
      "c.changeVariable1 " + (c.changeVariable1 ? "exists" : "undefined") + "'n" +
      "c.getInfo()=" + c.getInfo() + "'n" +
      "c.getLongInfo()=" + c.getLongInfo()
   );
}

如果有帮助：http://a-web.me/tutorial_javascript.html

很抱歉这个问题不准确。我知道javascript中的继承原则。我对指定库中的继承实现感兴趣。它有效，我测试了它。

图书馆是免费的，但它有一个封闭的代码，无法阅读它。它适用于所有浏览器。

我将指定的代码包装到html页面中，请查看。

<!DOCTYPE HTML>
<html>
<head>
    <title>Sample project</title>
    <!-- Styles -->
    <link rel="stylesheet" type="text/css" href="http://a-web.me/styles/default/a-web.css" >
    <!-- Scripts -->
    <script type="text/javascript" src="http://a-web.me/scripts/a-web.js"></script>
</head>
<body>
    <script type="text/javascript">
        /**
          * A-class
          */
        var ClassA = AWeb.class({
           public : {
              /**
                * A-class constructor
                */
              constructor : function() {
                 /* Private variable */
                 this.variable1 = "A";
                 this.calls = 0;
              },
              /**
                * Function returns information about the object
                */
              getInfo : function() {
                 this.incCalls();
                 return "variable1=" + this.variable1 + ", calls=" + this.calls;
              }
           },
           protected : {
              /**
                * Protected function
                */
              changeVariable1 : function( value ) {
                 this.variable1 = value;
              }
           },
           private : {
              /**
                * Private function
                */
              incCalls : function() {
                 this.calls++;
              }
           }
        });
        /**
          * C-class
          */
        var ClassC = AWeb.class({
           extends : ClassA,
           public : {
              /**
                * B-class constructor
                */
              constructor : function() {
                 this.super();
                 this.changeVariable1( "C" );
              },
              /**
                * Function returns extended information about the object
                */
              getLongInfo : function() {
                 return this.incCalls !== undefined ? "incCalls visible" : "incCalls undefined";
              }
           }
        });
        /**
          * Main project function
          */
        function main() {
           var a = new ClassA(),
               c = new ClassC();
           alert(
              "a instanceof ClassA: " + (a instanceof ClassA) + "'n" +
              "a instanceof ClassC: " + (a instanceof ClassC) + "'n" +
              "a.getInfo " + (a.getInfo ? "exists" : "undefined") + "'n" +
              "a.getLongInfo " + (a.getLongInfo ? "exists" : "undefined") + "'n" +
              "a.changeVariable1 " + (a.changeVariable1 ? "exists" : "undefined") + "'n" +
              "a.getInfo()=" + a.getInfo() + "'n'n" +
              "c instanceof ClassA: " + (c instanceof ClassA) + "'n" +
              "c instanceof ClassC: " + (c instanceof ClassC) + "'n" +
              "c.getInfo " + (c.getInfo ? "exists" : "undefined") + "'n" +
              "c.getLongInfo " + (c.getLongInfo ? "exists" : "undefined") + "'n" +
              "c.changeVariable1 " + (c.changeVariable1 ? "exists" : "undefined") + "'n" +
              "c.getInfo()=" + c.getInfo() + "'n" +
              "c.getLongInfo()=" + c.getLongInfo()
           );
        }
    </script>
</body>
</html>
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