javascript - 设置对象原型（示例）

Question

我正在尝试从“java脚本-理解奇怪的部分”课程中理解示例。解释说，当Greeter.init.prototype设置为时，Greeter.prototype它是为了更清晰的代码目的，所以我们可以在Greeter.prototype. 但是当尝试没有该设置的代码时 - 将我的方法直接存储Greeter.init.prototype在控制台中时出现错误：

未捕获的类型错误：无法设置未定义的属性“原型”

这是为什么？

• 示例工作部分：

（函数（全局，$）{

var Greeter = function (firstName){
    return new Greeter.init (firstName); 
}

Greeter.prototype = {};

Greeter.init = function (firstName){

    var self = this;
    self.firstName = firstName
}

Greeter.init.prototype = Greeter.prototype;

})(窗口, jQuery);

• 更改部分出错（第 7 行和第 15 行）：

（函数（全局，$）{

var Greeter = function (firstName){
    return new Greeter.init (firstName); 
}

Greeter.init.prototype = {};

Greeter.init = function (firstName){

    var self = this;
    self.firstName = firstName
}

})(窗口, jQuery);

标签： javascript

Answer 1

init您正在设置尚未初始化的属性 ( ) 的原型。

var Greeter = function (firstName){
    // also don't put spaces before parentheses of function calls
    return new Greeter.init(firstName); 
}

// Greeter.init is undefined here - so it throws
Greeter.init.prototype = {};

Greeter.init = function (firstName){

    var self = this;
    self.firstName = firstName
}

您应该首先初始化 init 并设置原型

var Greeter = function (firstName) {
    // also don't put spaces before parentheses of function calls
    return new Greeter.init(firstName); 
}

Greeter.init = function (firstName) {
    var self = this;
    self.firstName = firstName
}

// Greeter.init is no longer undefined
Greeter.init.prototype = {};