在面向对象的程序设计语言中，多态是继数据抽象和继承之后的第三个基本特征。
将一个方法调用同一个方法主体关联起来称作绑定，程序在运行时能从对象提供的信息中获取对象的类型，从而调用正确的方法体，所以也称为运行时绑定，后期绑定。
多态意味着“不同的形态”，就是对于继承自同一基类的不同子类对象，在相同的接口方法被调用时，会在运行时找到方法相对应的方法体。多态是跟继承协同工作的，是以继承为基础的。
在java中，除了static方法和final方法(private方法也是属于final方法)之后，其他所有的方法都是后期绑定的，通过后期绑定实现多态。这也就是说对于普通的方法调用可以是多态的，而对于静态方法和属性字段则不存在多态。
在继承时，只有public、protected和包可见的方法会被重载，对于基类中的private的方法是不会被子类覆盖的，对于子类而言，是不知道父类中是否有同名的private方法的，子类中同名的private方法就是一个完全不相关的全新方法。
<script type="text/javascript" charset="utf-8">
function doc (argument) {
document.write(argument);
document.write("<br />\n");
}
Object.extend(String, {
win: doc('this is object of Window ? ' + (this instanceof Window)), // true
size: function (str) {
return arguments.callee.print(str);
}
});
String.size.print = function (arg) {
//doc('String.size.print() = ' + arg.length);
return arg.length;
};
var s = "string size";
doc('String.size = ' + String.size(s));
doc(String.size.print(s));
var wStr = $w('a b c d e f g');
doc(wStr.inspect());
</script>
<script type="text/javascript" charset="utf-8">
function doc (argument) {
document.write(argument);
document.write("<br /><br />\n");
}
Object.extend = function(destination, source) {
for (var property in source) {
destination[property] = source[property];
}
return destination;
}
var o = {
test: 'test it',
sex: 'man',
info: function () {
return this.test + " and " + this.sex;
},
ivk: function () {
return this.info.apply(this); // invoke this.info function
}
}
for(var p in Object) {
doc('Object["' + p + '"] = ' + Object[p]);
}
doc("=============================================================");
Object.extend(Object, o);
for(var p in Object) {
doc('Object["' + p + '"] = ' + Object[p]);
}
alert(Object.ivk());
</script>
<script type="text/javascript" charset="utf-8">
function doc (argument) {
document.write(argument);
document.write("<br />\n");
}
doc((255).toColorPart());
doc((3).succ());
(5).times(function (i) {
doc(i);
})
</script>
<form action="form_submit" id="f1" method="post" accept-charset="utf-8">
<p><input type="text" name="test1" value="test1" id="test1"></p>
<p><input type="text" name="test2" value="test2" id="test2"></p>
<p>
<select id="s1" name="s1">
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
</select>
</p>
<p><input type="submit" value="submit"></p>
</form>
<script type="text/javascript" charset="utf-8">
function doc(argument) {
document.write("<p>\n");
document.write(argument);
document.write("</p>\n");
}
//Form.disable('f1');
Form.focusFirstElement('f1');
doc($('s1').type);// select-one
</script>
<div id="d1">replace</div>
<div id="d11" class="c1 c2 c3">x</div>
<div id="d10">xx</div>
<div id="d20">y</div>
<div id="d3">test</div>
<form action="index" method="post" id="f1" accept-charset="utf-8" style="background: #ddd; border: #ccc double 1px;">
<input type="text" name="input1" value="origin is enabled" id="input1">element.disable()<br/>
<input type="text" name="input2" value="origin is disabled" id="input2" disabled="true">element.enable()<br/>
<input type="text" name="input3" value="test activate()" id="input3">element.activate()<br/>
<input type="text" name="input4" value="test clear" id="input4">element.clear()<br/>
<input type="text" name="input5" value="test present(id input5)" id="input5">element.present()<br/>
<input type="text" name="input6" value="test serialize()" id="input6">element.serialize()<br/>
<input type="text" name="input7" value="test focus()" id="input7">element.focus()<br/>
<input type="text" name="input8" value="test select()" id="input8">element.select()<br/>
<input type="submit" value="Continue →"><br/>
</form>
<div id="d4">test Element scrollTo()</div>
<div id="d5">test element scrollTo()</div>
<div id="image">
<%= image_tag 'rails' %>
</div>
<script type="text/javascript" charset="utf-8">
function doc(argument) {
document.write("<p>\n");
document.write(argument);
document.write("</p>\n");
}
$('input1').disable();
$('input2').enable();
//$('input3').activate();
$('input4').clear();
doc('$("input5").present() = ' + $('input5').present());
doc('$("input6").serialize() is: ' + $('input6').serialize());
//$('input7').focus();
$('input8').select();
doc('form action is: ' + $('f1').readAttribute('action'));
doc('style of form: ' + $('f1').readAttribute('style'));
doc('getStyle background of form: ' + $('f1').getStyle('background'));
var cn = new Element.ClassNames('d11');
cn.add('c4');
cn.remove('c2');
Element.update('d10', 'test<strong> Element.update(element, "HTML") </strong>');
$('d20').update('test<strong> element.update("HTML") </strong>');
Element.replace('d1', '<div id="d2"><span>replaced div</span></div>');
doc(Element.inspect('d2'));
doc(Element.ancestors('d2').inspect().escapeHTML());
doc(Element.descendants('d2').inspect().escapeHTML());
doc(Element.previousSiblings('d3').inspect().escapeHTML());
doc(Element.nextSiblings('d3').inspect().escapeHTML());
Element.setOpacity('image', 0.6);
doc($('image').getOpacity());
$H(Element.Methods).each (function (m) {
doc(m);
});
doc($H(Element.getDimensions('d4')).inspect().escapeHTML());
// Element.scrollTo('d4');
$('f1').scrollTo();
doc("$('d5').empty() is: " + $('d5').empty());
var timer1 = setTimeout(function () {
$('d5').replace('<div id="d5">replace timer1</div>');
}, 5000);
var timer2 = setTimeout(function () {
$('d5').replace('<div id="d5">timeout d5</div>');
}, 15000);
$('f1').request({onComplete: function (xhr) {
alert(xhr.responseText);
}});
</script>
<script type="text/javascript" charset="utf-8">
function doc (argument) {
document.write(argument);
document.write("<br />\n");
}
var Class = {
create: function() {
return function() {
this.initialize.apply(this, arguments);
}
}
}
var MyClass = Class.create();
MyClass.prototype = {
initialize: function (msg) {
this.msg = msg;
return msg;
},
showMsg: function () {
doc(this.msg);
}
}
var c = new MyClass('test'); // Class.create('test')
c.showMsg();
var o = {
name: 'test it',
sex: 'man',
info: function () {
return this.name + " and " + this.sex;
},
ivk: function () {
return this.info.apply(this); // invoke this.info function
}
}
doc(o.info());
doc(o.ivk());
/*function TestThis () {
doc(this); // object Window
this.name = 'name test';
this.sex = 'name man';
}
var t = TestThis();
doc(name);
doc(self.name);
doc(this.sex);
for (var p in this) {
doc(this['p']);
}*/
</script>
<script type="text/javascript" src="prototype.js" charset="utf-8"></script>
<input type="checkbox" id="myChk" value="1"/> Test Function.prototype.bindAsEventListener
<input type="button" id="myBut1" value="bind element test" onclick="doc.bind(this)('arg1', 'arg2');"/> Test Function.prototype.bind
<input type="button" id="myBut2" value="bind window test" onclick="doc.bind(self)('arg1');"/> Test Function.prototype.bind
<script type="text/javascript" charset="utf-8">
function doc(){
// this 根据调用它的对象不同而不同，可以是element对象, 也可以是当前window对象
alert([this].concat($A(arguments)).inspect());
}
//declaring the class
var CheckboxWatcher = Class.create();
//defining the rest of the class implementation
CheckboxWatcher.prototype = {
initialize: function(chkBox, message) {
this.chkBox = $(chkBox);
this.message = message;
//this.chkBox.onclick
// = this.showMessage.bindAsEventListener(this, ' other extraInfo')
// => function(event) { return __method.apply(object, [event || window.event].concat(args));}
//将showMessage方法做为this object的方法来调用并返回showMessage方法的结果
//既然是将showMessage做为this object的方法来调用，那showMessage中的this是指向当前调用它的object(即为CheckboxWatcher的实例对象，如watcher)。
//this.chkBox.onclick = this.showMessage.apply(this, ['none event', ' other extraInfo']);
//assigning our method to the event
this.chkBox.onclick = this.showMessage.bindAsEventListener(this, ' other extraInfo');
},
showMessage: function(evt, extraInfo) {
//this是指向watcher这个实例对象的
//showMessage这个方法一般是不会从外部调用的
alert(this.message + ' (' + evt + ')' + extraInfo);
},
bindExample: function() {
alert(this.message + "\n" + $A(arguments).inspect);
}
};
var watcher = new CheckboxWatcher('myChk', 'Changed');
</script>
