我知道这是可行的:
function Foo() {};
Foo.prototype.talk = function () {
alert('hello~\n');
};
var a = new Foo;
a.talk(); // 'hello~\n'
但如果我想打电话
Foo.talk() // this will not work
Foo.prototype.talk() // this works correctly
我找到了一些制作Foo的方法。谈工作,
Foo。__proto__ = Foo.prototype Foo。talk = Foo.prototype.talk
还有别的办法吗?我不知道这样做是否正确。在JavaScript代码中使用类方法还是静态方法?
当前回答
另外，现在可以用类和静态来做
'use strict'
class Foo {
static talk() {
console.log('talk')
};
speak() {
console.log('speak')
};
};
将会给
var a = new Foo();
Foo.talk(); // 'talk'
a.talk(); // err 'is not a function'
a.speak(); // 'speak'
Foo.speak(); // err 'is not a function'
其他回答
另外，现在可以用类和静态来做
'use strict'
class Foo {
static talk() {
console.log('talk')
};
speak() {
console.log('speak')
};
};
将会给
var a = new Foo();
Foo.talk(); // 'talk'
a.talk(); // err 'is not a function'
a.speak(); // 'speak'
Foo.speak(); // err 'is not a function'
我使用命名空间:
var Foo = {
element: document.getElementById("id-here"),
Talk: function(message) {
alert("talking..." + message);
},
ChangeElement: function() {
this.element.style.color = "red";
}
};
要使用它:
Foo.Talk("Testing");
Or
Foo.ChangeElement();
下面是一个很好的例子来演示Javascript如何处理静态/实例变量和方法。
function Animal(name) {
Animal.count = Animal.count+1||1;// static variables, use function name "Animal"
this.name = name; //instance variable, using "this"
}
Animal.showCount = function () {//static method
alert(Animal.count)
}
Animal.prototype.showName=function(){//instance method
alert(this.name);
}
var mouse = new Animal("Mickey");
var elephant = new Animal("Haddoop");
Animal.showCount(); // static method, count=2
mouse.showName();//instance method, alert "Mickey"
mouse.showCount();//Error!! mouse.showCount is not a function, which is different from Java
如果你必须在ES5中编写静态方法，我找到了一个很棒的教程:
//Constructor
var Person = function (name, age){
//private properties
var priv = {};
//Public properties
this.name = name;
this.age = age;
//Public methods
this.sayHi = function(){
alert('hello');
}
}
// A static method; this method only
// exists on the class and doesn't exist
// on child objects
Person.sayName = function() {
alert("I am a Person object ;)");
};
看到@https: / / abdulapopoola.com/2013/03/30/static-and-instance-methods-in-javascript/
只是额外的注释。使用类ES6，当我们创建静态方法时，javacscript引擎设置的描述符属性与老式的“静态”方法略有不同
function Car() {
}
Car.brand = function() {
console.log('Honda');
}
console.log(
Object.getOwnPropertyDescriptors(Car)
);
它将brand()的内部属性(描述符属性)设置为
..
brand: [object Object] {
configurable: true,
enumerable: true,
value: ..
writable: true
}
..
相比
class Car2 {
static brand() {
console.log('Honda');
}
}
console.log(
Object.getOwnPropertyDescriptors(Car2)
);
将brand()的内部属性设置为
..
brand: [object Object] {
configurable: true,
enumerable: false,
value:..
writable: true
}
..
在ES6中static method的enumerable设置为false。
这意味着你不能使用for-in循环来检查对象
for (let prop in Car) {
console.log(prop); // brand
}
for (let prop in Car2) {
console.log(prop); // nothing here
}
静态方法在ES6中被视为其他类的私有属性(名称，长度，构造函数)，除了静态方法仍然是可写的，因此描述符writable被设置为true {writable: true}。这也意味着我们可以推翻它
Car2.brand = function() {
console.log('Toyota');
};
console.log(
Car2.brand() // is now changed to toyota
);
