Question

我想在javascript中覆盖内部函数。这是代码：

function Menu(x, y, z) {    
  this.createMenu = function(x, y) {
    //Some functionality
  }    
}

我想覆盖createMenu函数而不覆盖完整的Menu函数。有没有办法这样做。

Answer 1

您可以在其实例中覆盖它。

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Answer 2

有两种可能的方法，一种是覆盖和覆盖原始构造函数和引入工厂的构造函数创建构造函数的实例，并重新分配新行为已经存在的财产。

采用后一种方法，一个是健全且安全的，但需要控制将所有代码出现次数new Menu( ... )更改为例如createModifiedMenu。

只有当一个人不想或根本不能改变那些提到的那些时代码出现，并且仅在某种类型的检查不依赖于操作时使用instanceof，应考虑采用前一种方法......

＆＃34;覆盖和包装＆＃34;方法......

//
//  closed implementation of code one does not own.
//
function Menu(x, y, z) {
    this.createMenu = function(x, y) {
        //Some functionality
    }
}

//
//  "overwriting and wrapping" approach.
//
Menu = (function (proceed) {

    function alternativeCreateMenu(x, y) {
        // alternative createMenu implementation
    }

    function ModifiedMenu(/*x, y, z*/) {
        // "restoration fake" of the original constructor.
        this.constructor = proceed;

        // super call via original constructor.
        proceed.apply(this, arguments);

        // altering the behavior.
        this.createMenu = alternativeCreateMenu;
    }
    // finsihing the inheritance step.
    ModifiedMenu.prototype = (new proceed);

    return ModifiedMenu;

}(Menu));


var menu = new Menu("a", "b", "c"); // ... thus, no instantiation shipped with
                                    // already existing code needs to be touched.
console.log("menu : ", menu);

工厂方法......

//
//  closed implementation of code one does not own.
//
function Menu(x, y, z) {
    this.createMenu = function(x, y) {
        //Some functionality
    }
}

//
//  factory approach.
//
var createModifiedMenu = (function (Menu) {

    function alternativeCreateMenu(x, y) {
        // alternative createMenu implementation
    }
    return function (x, y, z) { // factory.
        var
            menu = new Menu(x, y, z);

        menu.createMenu = alternativeCreateMenu;

        return menu;
    };
}(Menu));


var menu = createModifiedMenu("a", "b", "c"); // ... thus, every instantiation shipped with
                                              // already existing code needs to be changed
console.log("menu : ", menu);                 // from `new Menu( ... )` to `createModifiedMenu( ... )`

在javascript中覆盖内部函数的行为

2 个答案: