(1)简化代码
<wbr></wbr>
JavaScript定义对象和数组非常简单,我们想要创建一个对象,一般是这样写的:<wbr><wbr></wbr></wbr>
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var
car =
new
Object();
car.colour =
'red'
;
car.wheels = 4;
car.hubcaps =
'spinning'
;
car.age = 4;
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下面的写法可以达到同样的效果:
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var
car = {
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
colour:
'red'
,
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
wheels:4,
hubcaps:
'spinning'
,
age:4
}
|
后面的写法要短得多,而且你不需要重复写对象名称。
另外对于数组同样有简洁的写法,过去我们声明数组是这样写的:
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var
moviesThatNeedBetterWrit<wbr>ers =</wbr>
new
Array(
<wbr><wbr></wbr></wbr>
'Transformers'
,
'Transformers2'
,
'Avatar'
,
'Indiana Jones 4'
);
|
更简洁的写法是:<wbr></wbr>
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var
moviesThatNeedBetterWrit<wbr>ers = [</wbr>
<wbr><wbr></wbr></wbr>
'Transformers'
,
'Transformers2'
,
'Avatar'
,
'Indiana Jones 4'
];
|
对于数组,还有关联数组这样一个特别的东西。<wbr>你会发现很多代码是这样定义对象的:</wbr>
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var
car =
new
Array();
car[
'colour'
] =
'red'
;
car[
'wheels'
] = 4;
car[
'hubcaps'
] =
'spinning'
;
car[
'age'
] = 4;
|
这太疯狂了,不要觉得困惑,“关联数组”只是对象的一个别名而已。
另外一个简化代码的方法是使用三元运算符,举个例子:
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var
direction;
if
(x < 200){
<wbr><wbr></wbr></wbr>
direction = 1;
}
else
{
<wbr><wbr></wbr></wbr>
direction = -1;
}
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我们可以使用如下的代码替换这种写法:
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var
direction = x < 200 ? 1 : -1;
|
<wbr></wbr>
<wbr></wbr>
(2)使用JSON作为数据格式 <wbr><wbr></wbr></wbr>
<wbr></wbr>
<wbr></wbr>
伟大的Douglas Crockford发明了JSON数据格式来存储数据,你可以使用原生的javascript方法来存储复杂的数据而不需要进行任何额外的转换,例如:
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var
band = {
<wbr><wbr></wbr></wbr>
"name"
:
"The Red Hot Chili Peppers"
,
<wbr><wbr></wbr></wbr>
"members"
:[
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
{
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"name"
:
"Anthony Kiedis"
,
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"role"
:
"lead vocals"
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
},
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
{
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"name"
:
"Michael 'Flea' Balzary"
,
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"role"
:
"bass guitar, trumpet, backing vocals"
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
},
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
{
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"name"
:
"Chad Smith"
,
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"role"
:
"drums,percussion"
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
},
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
{
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"name"
:
"John Frusciante"
,
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
"role"
:
"Lead Guitar"
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
}
<wbr><wbr></wbr></wbr>
],
<wbr><wbr></wbr></wbr>
"year"
:
"2009"
}
|
你可以使用在JavaScript中直接使用JSON,甚至作为API返回的一种格式,在许多的API中被应用,例如:
<wbr></wbr>
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<
div
id
=
"delicious"
></
div
><
script
>
function delicious(o){
<wbr><wbr></wbr></wbr>
var out = '<
ul
>';
<wbr><wbr></wbr></wbr>
for(var i=0;i<
o.length
;i++){
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
out += '<li><
a
href
=
"' + o[i].u + '"
>' +
<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
o[i].d + '</
a
></
li
>';
<wbr><wbr></wbr></wbr>
}
<wbr><wbr></wbr></wbr>
out += '</
ul
>';
<wbr><wbr></wbr></wbr>
document.getElementByIdx_x('delicious').innerHTML = out;
}
</
script
>
<
script
src
=
"http://feeds.delicious.com/v2/json/codepo8/javascript?count=15&callback=delicious"
></
script
>
|
这里调用delicious 的Web服务获取最新书签,以JSON格式返回,然后将它们显示成无序列表的形式。
从本质上讲,JSON是用于描述复杂的数据最轻量级的方式,而且直接它运行在浏览器中。<wbr>你甚至可以在PHP中调用 json_decode()函数来使用它。</wbr>
(3)尽量使用JavaScript原生函数<wbr></wbr>
<wbr></wbr>
要找一组数字中的最大数,我们可能会写一个循环,例如:
<wbr></wbr>
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var
numbers = [3,342,23,22,124];
var
max = 0;
for
(
var
i=0;i<numbers.length;i++){
<wbr><wbr></wbr></wbr>
if
(numbers[i] > max){
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
max = numbers[i];
<wbr><wbr></wbr></wbr>
}
}
alert(max);
|
其实,不用循环可以实现同样的功能:
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var
numbers = [3,342,23,22,124];
numbers.sort(
function
(a,b){
return
b - a});
alert(numbers[0]);
|
而最简洁的写法是:
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Math.max(12,123,3,2,433,4);
// returns 433
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你甚至可以使用Math.max来检测浏览器支持哪个属性:
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var
scrollTop= Math.max(
<wbr></wbr>
doc.documentElement.scrollTop,
<wbr></wbr>
doc.body.scrollTop
);
|
如果你想给一个元素增加class样式,可能原始的写法是这样的:
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function
addclass(elm,newclass){
<wbr><wbr></wbr></wbr>
var
c = elm.className;
<wbr><wbr></wbr></wbr>
elm.className = (c ===
''
) ? newclass : c+
' '
+newclass;
|
而更优雅的写法是:
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function
addclass(elm,newclass){
<wbr><wbr></wbr></wbr>
var
classes = elm.className.split(
' '
);
<wbr><wbr></wbr></wbr>
classes.push(newclass);
<wbr><wbr></wbr></wbr>
elm.className = classes.join(
' '
);
}
|
<wbr></wbr>
(4)事件委托
<wbr></wbr>
事件是JavaScript非常重要的一部分。我们想给一个列表中的链接绑定点击事件,一般的做法是写一个循环,给每个链接对象绑定事件,HTML代码如下:
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<h2>Great Web resources</h2>
<ul id=
"resources"
>
<wbr><wbr></wbr></wbr>
<li><a href=
"http://blameitonthevoices.com"
>Blame it on the voices</a></li>
</ul>
|
脚本如下:
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// Classic event handling example
(
function
(){
<wbr><wbr></wbr></wbr>
var
resources = document.getElementByIdx_x(
'resources'
);
<wbr><wbr></wbr></wbr>
var
links = resources.getElementsByTagName_r(
'a'
);
<wbr><wbr></wbr></wbr>
var
all = links.length;
<wbr><wbr></wbr></wbr>
for
(
var
i=0;i<all;i++){
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
// Attach a listener to each link
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
links[i].addEventListener(
'click'
,handler,
false
);
<wbr><wbr></wbr></wbr>
};
<wbr><wbr></wbr></wbr>
function
handler(e){
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
var
x = e.target;
// Get the link that was clicked
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
alert(x);
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
e.preventDefault();
<wbr><wbr></wbr></wbr>
};
})();
|
更合理的写法是只给列表的父对象绑定事件,代码如下:
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(
function
(){
<wbr><wbr></wbr></wbr>
var
resources = document.getElementByIdx_x(
'resources'
);
<wbr><wbr></wbr></wbr>
resources.addEventListener(
'click'
,handler,
false
);
<wbr><wbr></wbr></wbr>
function
handler(e){
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
var
x = e.target;
// get the link tha
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
if
(x.nodeName.toLowerCase() ===
'a'
){
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
alert(
'Event delegation:'
+ x);
<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>
e.preventDefault();
<wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr>
}
<wbr><wbr></wbr></wbr>
};
})();
|
<wbr></wbr>
(5)匿名函数
<wbr></wbr>
关于JavaScript的最头疼的事情之一是,它的变量没有特定的作用范围。<wbr>一般情况下,任何变量,函数,数组或对象都是全局性,这意味着在同一页上的其他脚本可以访问并覆盖它们。解决方法是把变量封装在一个匿名函数中。<wbr>例如,下面的定义将产生三个全局变量和和两个全局函数: <div> <div> <div javascript=""> <div><a href="http://www.cnblogs.com/lhb25/archive/2011/01/10/1932284.html#">?</a></div> <table cellspacing="0" cellpadding="0" border="0"><tbody><tr> <td> <div index0="" number1="">1</div> <div index1="" number2="">2</div> <div index2="" number3="">3</div> <div index3="" number4="">4</div> <div index4="" number5="">5</div> <div index5="" number6="">6</div> <div index6="" number7="">7</div> <div index7="" number8="">8</div> <div index8="" number9="">9</div> </td> <td> <div> <div index0="" number1=""> <code>var</code> <code>name =</code> <code>'Chris'</code><code>;</code> </div> <div index1="" number2=""> <code>var</code> <code>age =</code> <code>'34'</code><code>;</code> </div> <div index2="" number3=""> <code>var</code> <code>status =</code> <code>'single'</code><code>;</code> </div> <div index3="" number4=""> <code>function</code> <code>createMember(){</code> </div> <div index4="" number5=""> <code><wbr><wbr></wbr></wbr></code><code>// [...]</code> </div> <div index5="" number6=""><code>}</code></div> <div index6="" number7=""> <code>function</code> <code>getMemberDetails(){</code> </div> <div index7="" number8=""> <code><wbr><wbr></wbr></wbr></code><code>// [...]</code> </div> <div index8="" number9=""><code>}</code></div> </div> </td> </tr></tbody></table> </div> </div> </div> <p>封装后如下:</p> <div> <div> <div javascript=""> <div><a href="http://www.cnblogs.com/lhb25/archive/2011/01/10/1932284.html#">?</a></div> <table cellspacing="0" cellpadding="0" border="0"><tbody><tr> <td> <div index0="" number1="">1</div> <div index1="" number2="">2</div> <div index2="" number3="">3</div> <div index3="" number4="">4</div> <div index4="" number5="">5</div> <div index5="" number6="">6</div> <div index6="" number7="">7</div> <div index7="" number8="">8</div> <div index8="" number9="">9</div> <div index9="" number10="">10</div> <div index10="" number11="">11</div> <div index11="" number12="">12</div> <div index12="" number13="">13</div> <div index13="" number14="">14</div> <div index14="" number15="">15</div> </td> <td> <div> <div index0="" number1=""> <code>var</code> <code>myApplication =</code> <code>function</code><code>(){</code> </div> <div index1="" number2=""> <code><wbr><wbr></wbr></wbr></code><code>var</code> <code>name =</code> <code>'Chris'</code><code>;</code> </div> <div index2="" number3=""> <code><wbr><wbr></wbr></wbr></code><code>var</code> <code>age =</code> <code>'34'</code><code>;</code> </div> <div index3="" number4=""> <code><wbr><wbr></wbr></wbr></code><code>var</code> <code>status =</code> <code>'single'</code><code>;</code> </div> <div index4="" number5=""> <code><wbr><wbr></wbr></wbr></code><code>return</code><code>{</code> </div> <div index5="" number6=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>createMember:</code><code>function</code><code>(){</code> </div> <div index6="" number7=""> <code><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></code><code>// [...]</code> </div> <div index7="" number8=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>},</code> </div> <div index8="" number9=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>getMemberDetails:</code><code>function</code><code>(){</code> </div> <div index9="" number10=""> <code><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></code><code>// [...]</code> </div> <div index10="" number11=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>}</code> </div> <div index11="" number12=""> <code><wbr><wbr></wbr></wbr></code><code>}</code> </div> <div index12="" number13=""><code>}();</code></div> <div index13="" number14=""><code>// myApplication.createMember() and</code></div> <div index14="" number15=""><code>// myApplication.getMemberDetails() now works.</code></div> </div> </td> </tr></tbody></table> </div> </div> </div> <p>这被称为单体模式,是JavaScript设计模式的一种,这种模式在YUI中用得非常多,改进的写法是: <wbr></wbr></p> <div> <div> <div javascript=""> <div><a href="http://www.cnblogs.com/lhb25/archive/2011/01/10/1932284.html#">?</a></div> <table cellspacing="0" cellpadding="0" border="0"><tbody><tr> <td> <div index0="" number1="">1</div> <div index1="" number2="">2</div> <div index2="" number3="">3</div> <div index3="" number4="">4</div> <div index4="" number5="">5</div> <div index5="" number6="">6</div> <div index6="" number7="">7</div> <div index7="" number8="">8</div> <div index8="" number9="">9</div> <div index9="" number10="">10</div> <div index10="" number11="">11</div> <div index11="" number12="">12</div> <div index12="" number13="">13</div> <div index13="" number14="">14</div> <div index14="" number15="">15</div> <div index15="" number16="">16</div> </td> <td> <div> <div index0="" number1=""> <code>var</code> <code>myApplication =</code> <code>function</code><code>(){</code> </div> <div index1="" number2=""> <code><wbr><wbr></wbr></wbr></code><code>var</code> <code>name =</code> <code>'Chris'</code><code>;</code> </div> <div index2="" number3=""> <code><wbr><wbr></wbr></wbr></code><code>var</code> <code>age =</code> <code>'34'</code><code>;</code> </div> <div index3="" number4=""> <code><wbr><wbr></wbr></wbr></code><code>var</code> <code>status =</code> <code>'single'</code><code>;</code> </div> <div index4="" number5=""> <code><wbr><wbr></wbr></wbr></code><code>function</code> <code>createMember(){</code> </div> <div index5="" number6=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>// [...]</code> </div> <div index6="" number7=""> <code><wbr><wbr></wbr></wbr></code><code>}</code> </div> <div index7="" number8=""> <code><wbr><wbr></wbr></wbr></code><code>function</code> <code>getMemberDetails(){</code> </div> <div index8="" number9=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>// [...]</code> </div> <div index9="" number10=""> <code><wbr><wbr></wbr></wbr></code><code>}</code> </div> <div index10="" number11=""> <code><wbr><wbr></wbr></wbr></code><code>return</code><code>{</code> </div> <div index11="" number12=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>create:createMember,</code> </div> <div index12="" number13=""> <code><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></code><code>get:getMemberDetails</code> </div> <div index13="" number14=""> <code><wbr><wbr></wbr></wbr></code><code>}</code> </div> <div index14="" number15=""><code>}();</code></div> <div index15="" number16=""><code>//myApplication.get() and myApplication.create() now work.</code></div> </div> </td> </tr></tbody></table> </div> </div> </div> <p><wbr><wbr></wbr></wbr></p> <p><strong>(</strong>6<strong>)代码可配置</strong></p> <hr> <p> 你写的代码如果想让别人更容易进行使用或者修改,则需要可配置,解决方案是在你写的脚本中增加一个配置对象。要点如下:<wbr><br><wbr><br> 1、在你的脚本中新增一个叫configuration的对象。</wbr></wbr></p> <p>2、在配置对象中存放所有其它人可能想要去改变的东西,例如CSS的ID、class名称、语言等等。</p> <p>3、返回这个对象,作为公共属性以便其它人可以进行重写。<wbr></wbr></p> <wbr><p><wbr></wbr></p> <p><strong>(</strong>7<strong>)代码兼容性</strong></p> <hr> <p> 兼容性是初学者容易忽略的部分,通常学习Javascript的时候都是在某个固定的浏览器中进行测试,而这个浏览器很有可能就是IE,这是非常致命的,因为目前几大主流浏览器中偏偏IE对标准的支持是最差的。最终用户看到的结果也许就是,你写的代码在某个浏览器无法正确运行。你应该把你的代码在主流的浏览器中都测试一下,这也许很费时间,但是应该这样做。<wbr><wbr></wbr></wbr></p> </wbr></wbr></wbr>