Question

我正在尝试在函数内创建方法。我可以这样做：

function sample() {};
sample.show = function() { alert() };

我会看到提醒sample.show();的提醒。但是由于代码美化的原因，我想在函数内部移动所有方法声明。我试过了：

function sample() {
    sample.show = function() { alert() };
}

但我明白了：TypeError: Object function sample() has no method 'show' 我尝试的另一种方式：

function sample() {
    this.show = function() { alert() };
}
function sample() {
    sample.prototype.show = function() { alert() };
}
function sample() {
    this.prototype.method = function show () { alert() };
}

但结果是一样的。我甚至找不到有关在函数内创建方法的任何信息。你能指出一个正确的方法吗？

UPD ：我希望能够调用sample()函数，它也可以执行某些操作。所以答案中还没有解决方案。

function sample() {
    this.show = function() { alert() };
    console.log('you called "sample()"');
}
sample(); // ==> you called "sample()"

Answer 1

首次尝试：

function sample() {
    sample.show = function() { alert() };
}

这只会创建一个＆＃34;静态＆＃34; sample函数上的方法，只有在执行后

console.log(sample.show);
//would show undefined on the console
sample();
console.log(sample.show);
//would then show the method definition as it has now been
//defined as a property of "sample"

第二次尝试：

function sample() {
    this.show = function() { alert() };
}

这仅在您创建示例

的实例时才有效

console.log(sample.show);
//will print undefined as there is no property "show" on sample
sample();
console.log(window.show);
//will print the function, but since sample was executed without a
//context, show is created as a property of the global object
//in this case "window"
var d = new sample();
console.log(d.show);
//will print the function as we now have a instance of sample which
//show was made a property of
console.log(sample.prototype.show);
//will show undefined as you are not actually creating the "show" method
//on the constructor sample's prototype

现在有了原型版本：

function sample() {
    sample.prototype.show = function() { alert() };
}

通过此操作，您将能够访问＆＃34; show＆＃34;方法要么通过实例，要么来自原型链，但是对于原型链调用来说，你必须至少先制作一个实例

console.log(sample.prototype.show);
//will print undefined as "show" has not been defined on the prototype yet
var d = new sample();
console.log(d.show);
console.log(sample.prototype.show);
//Both will now print the function because the method has been defined

然而最后一个：

function sample() {
    this.prototype.method = function show () { alert() };
}

根本无法正常工作，因为您无法直接从实例访问原型，一旦您尝试创建实例，您将收到未定义的错误。

要使它工作，你必须通过构造函数链来设置方法

function sample() {
    this.constructor.prototype.method = function show () { alert() };
    //is the same as doing
    sample.prototype.method = function show(){ alert() };
}

总的来说，你的美化＆＃34;为了工作，你必须先直接调用sample，直接调用第一个，或者为其他人创建一个实例。

Answer 2

在调用sample之前，不会执行sample函数中的代码。所以你可以通过这样做来让你的榜样起作用：

function sample() {
    sample.show = function() { alert() };
}

sample()
sample.show()

Answer 3

你可以试试这个：

function sample() {
    this.show = function() { alert() };
}

var x = new sample();
x.show();

Answer 4

您需要将样本设为对象

var sample = {
  this.show = function() { alert() };
}

在函数内创建方法

4 个答案: