如何在JavaScript中制作课程？

Question

在JavaScript中有很多方法可以完成相同的操作。但是，我已经掌握了一些方式，但坦率地说，有些方式我不理解。有人可以帮我澄清一些事情吗？（我首先在PHP中学习了OOP。）

所以可以这样制作一个类：

var object = new class(constructparams) {
    var private_members; // Can be accessed from within the code inside this definition only.
    this.public_members; // Can be accessed from everywhere.

    var private_functions = function() {}
    this.public_functions = function() {}
}

object.prototype.semi_public_members = function() {
    // Will be public, but can only access public members and methods.
    // E. g. private_members; is not available here.
}

到目前为止，这一切正确吗？

然后有人喜欢使用自执行匿名函数方法来创建名称空间。这样做的目的是什么，当您在上面做同样的事情时，提供了一个命名空间？

最后，您有一个我不理解的对象文字符号。

var object = { // Something strange in here }

那里发生了什么事？是JSON吗？如何使用，如何使用。用这种方式代替我描述的方法有什么好处？您为什么要原型而不是第一次进行正确的分类？

Answer 1

通过示例解释 构造对象 中不同事物的行为：

// Defined as a variable from an anonymous function
// so that there is scope closure over variables
// shared across all instances and the prototype.
// If this isn't important, you don't need to close
// scope around it, so define directly
var ConstructedObject = (function constructorCreator () {
    // Define any variables/methods to be shared across
    // all instances but not polluting the namespace
    var sharedVariable = 'foo';

    // Next the actual constructor
    function ConstructedObject () {
        // Variables here are normally used to help
        // each instance and will be kept in memory as
        // long as the instance exists
        var instanceVariable = 'bar';
        // instance-specific properties get defined
        // using the "this" keyword, these are the
        // properties expected to be changed across
        // each different instance
        this.instanceProperty = true;
        this.instanceMethod = function () { return instanceVariable; };
        this.changeInstanceVar = function () { instanceVariable = 'foo'; };
            // you do have access to the shared
            // variables here if you need them.
    }
    // After the constructor, you set up the
    // prototype, if any. This is an object of shared
    // properties and methods to be inherited by every
    // instance made by the constructor, and it also
    // inherits the prototype's prototype, too.
    // Lets use a literal object for simplicity.
    ConstructedObject.prototype = {
        // Accessing the instance to which a method
        // applies is done using the "this" keyword,
        // similar to in the constructor
        sharedMethod : function () { return [sharedVariable, this.instanceMethod(),this.instanceProperty]; },
        changeSharedVar : function () { sharedVariable = 'bar'; }
        // properties may also be defined
    };
    // Finally, the constructor is returned so it
    // can be kept alive outside of the anonymous
    // function used to create it
    return ConstructedObject;
// and the anonymous function is called to execute
// what we've done so far
})();

执行上述代码后，您将拥有一个构造器，该构造器创建具有实例特定变量和共享变量的对象。现在，通过创建两个实例并在进行一些更改之前和之后进行比较来查看它们的行为。

// First create the two instances
var myObjA = new ConstructedObject(),
    myObjB = new ConstructedObject();
// Now compare them, the sharedMethod method we
// used in the prototype offers an easy way to
// do this
console.log( myObjA.sharedMethod(), myObjB.sharedMethod() );
// ["foo", "bar", true] ["foo", "bar", true]
// Next lets change the different variables in
// myObjB so we can see what happens, again the
// change* methods defined before let us do this
// easily
myObjB.changeInstanceVar();
myObjB.changeSharedVar();
// For completeness, lets also change the property
// on myObjB.
myObjB.instanceProperty = false;
// Now when we compare them again, we see that our
// changes to the myObjB instance have only changed
// the shared variables of myObjA
console.log( myObjA.sharedMethod(), myObjB.sharedMethod() );
// ["bar", "bar", true] ["bar", "foo", false]

这是两个已记录的语句，以便于查看

//     myObjA               myObjB
["foo", "bar", true] ["foo", "bar", true]
["bar", "bar", true] ["bar", "foo", false]