JavaScript类/对象可以有构造函数吗?它们是如何产生的?
当前回答
在大多数情况下,在调用传递此信息的方法之前,必须以某种方式声明所需的属性。如果你不需要一开始就设置一个属性,你可以像这样在对象中调用一个方法。可能不是最漂亮的方法,但这仍然有效。
var objectA = {
color: '';
callColor : function(){
console.log(this.color);
}
this.callColor();
}
var newObject = new objectA();
其他回答
这种模式对我很有帮助。使用这种模式,你在单独的文件中创建类,“根据需要”将它们加载到整个应用程序中。
// Namespace
// (Creating new if not instantiated yet, otherwise, use existing and just add to it)
var myApp = myApp || {};
// "Package"
// Similar to how you would establish a package in other languages
(function() {
// "Class"
var MyClass = function(params) {
this.initialize(params);
}
// "Private Static" vars
// - Only accessible to functions in this class.
// - Doesn't get wiped out when we create a new instance.
var countInstances = 0;
var allInstances = [];
// "Private Static" functions
// - Same as above, but it's a function accessible
// only to other functions in this class.
function doSomething(){
}
// "Public Static" vars
// - Everyone has access.
// - Doesn't get wiped out when we create a new instance.
MyClass.counter = 0;
// "Public Static" functions
// - Same as above, but anyone can call this "static method".
// - Kinda like a singleton class situation.
MyClass.foobar = function(){
}
// Public properties and methods are built into the "prototype"
// - This is how each instance can become unique unto itself.
// - Establishing "p" as "local" (Static Private) variable
// simply so we don't have to keep typing "MyClass.prototype"
// for each property and function.
var p = MyClass.prototype;
// "Public" vars
p.id = null;
p.firstname = null;
p.lastname = null;
// "Private" vars
// - Only used by "this" instance.
// - There isn't "true" privacy for each
// instance so we have to fake it.
// - By tradition, we indicate "privacy"
// by prefixing it with an underscore.
// - So technically, anyone can access, but we simply
// don't tell anyone about it (e.g. in your API)
// so no one knows about it :)
p._foo = null;
p.initialize = function(params){
this.id = MyClass.counter++;
this.firstname = params.firstname;
this.lastname = params.lastname;
MyClass.counter++;
countInstances++;
allInstances.push(this);
}
p.doAlert = function(theMessage){
alert(this.firstname + " " + this.lastname + " said: " + theMessage + ". My id:" + this.id + ". Total People:" + countInstances + ". First Person:" + allInstances[0].firstname + " " + allInstances[0].lastname);
}
// Assign class to app
myApp.MyClass = MyClass;
// Close the "Package"
}());
// Usage example:
var bob = new myApp.MyClass({ firstname : "bob",
lastname : "er"
});
bob.doAlert("hello there");
http://www.jsoops.net/对于Js中的oop非常好。提供私有、受保护、公共变量和函数,并具有继承特性。示例代码:
var ClassA = JsOops(function (pri, pro, pub)
{// pri = private, pro = protected, pub = public
pri.className = "I am A ";
this.init = function (var1)// constructor
{
pri.className += var1;
}
pub.getData = function ()
{
return "ClassA(Top=" + pro.getClassName() + ", This=" + pri.getClassName()
+ ", ID=" + pro.getClassId() + ")";
}
pri.getClassName = function () { return pri.className; }
pro.getClassName = function () { return pri.className; }
pro.getClassId = function () { return 1; }
});
var newA = new ClassA("Class");
//***Access public function
console.log(typeof (newA.getData));
// function
console.log(newA.getData());
// ClassA(Top=I am A Class, This=I am A Class, ID=1)
//***You can not access constructor, private and protected function
console.log(typeof (newA.init)); // undefined
console.log(typeof (newA.className)); // undefined
console.log(typeof (newA.pro)); // undefined
console.log(typeof (newA.getClassName)); // undefined
只是为了提供一些变化。ds。Oop是一种在javascript中使用构造函数声明类的好方法。它支持所有可能的继承类型(包括一种甚至c#都不支持的类型)以及很好的接口。
var Color = ds.make.class({
type: 'Color',
constructor: function (r,g,b) {
this.r = r; /* now r,g, and b are available to */
this.g = g; /* other methods in the Color class */
this.b = b;
}
});
var red = new Color(255,0,0); // using the new keyword to instantiate the class
使用原型:
function Box(color) // Constructor
{
this.color = color;
}
Box.prototype.getColor = function()
{
return this.color;
};
隐藏“color”(有点像私有成员变量):
function Box(col)
{
var color = col;
this.getColor = function()
{
return color;
};
}
用法:
var blueBox = new Box("blue");
alert(blueBox.getColor()); // will alert blue
var greenBox = new Box("green");
alert(greenBox.getColor()); // will alert green
在大多数情况下,在调用传递此信息的方法之前,必须以某种方式声明所需的属性。如果你不需要一开始就设置一个属性,你可以像这样在对象中调用一个方法。可能不是最漂亮的方法,但这仍然有效。
var objectA = {
color: '';
callColor : function(){
console.log(this.color);
}
this.callColor();
}
var newObject = new objectA();