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面對對象的編程

1.引用傳遞

在javascript中,string int Boolean 不是按引用進行傳遞的.而對象和數組是按引用傳遞的.

示例:

?//?Create?an?array?of?items
var?items?=?new?Array("one",?"two",?"three");
//?Create?a?reference?to?the?array?of?items
var?itemsRef?=?items;
//?Add?an?item?to?the?original?array
items.push("four");
//?The?length?of?each?array?should?be?the?same,
//?since?they?both?point?to?the?same?array?object
alert(items.length?==?itemsRef.length); 結果是 true

2.每一個Function中都有一個上下文變量arguments,它是一個偽數組(不可以改變).它代表著當前Function的參數列表.

?在javascript中,變量的作用域是整個Function,而不是{}.這點有別于c#等其他語言.

//?Set?a?global?variable,?foo,?equal?to?test
var?foo?=?"test";
//?Within?an?if?block
if?(true)?{
//?Set?foo?equal?to?'new?test'
//?NOTE:?This?is?still?within?the?global?scope!
var?foo?=?"new?test";
}
//?As?we?can?see?here,?as?foo?is?now?equal?to?'new?test'
alert(foo?==?"new?test");
//?Create?a?function?that?will?modify?the?variable?foo
function?test()?{
var?foo?=?"old?test";
}
//?However,?when?called,?'foo'?remains?within?the?scope
//?of?the?function
test();
//?Which?is?confirmed,?as?foo?is?still?equal?to?'new?test'
alert(foo?==?"new?test");

// A globally-scoped variable, containing the string 'test'

var test = "test";

// You'll notice that our 'global' variable and the test

// property of the the window object are identical

alert( window.test == test );

全局變量可以理解為window的屬性.

編寫javascript代碼時的一些注意事項:

要對使用的變量進行聲明.以避免不同的作用域時的沖突.

理解0 false ‘’ undefined null 這些值在javascript里是相同的,都等于false.

// Both of these are true

null == false

0 == undefined

// You should use !== or === instead

null !== false

false === false

DOM 編程

<p><strong>Hello</strong> how are you doing?</p>

使用DOM的時候,小心一些空白(text)造成的影響,經常使你能找到自己想要的目標元素. function cleanWhitespace( element ) {

// If no element is provided, do the whole HTML document

element = element || document;

// Use the first child as a starting point

var cur = element.firstChild;

// Go until there are no more child nodes

while ( cur != null ) {

// If the node is a text node, and it contains nothing but whitespace

if ( cur.nodeType == 3 && ! /\S/.test(cur.nodeValue) ) {

// Remove the text node

element.removeChild( cur );

// Otherwise, if it's an element

} else if ( cur.nodeType == 1 ) {

// Recurse down through the document

cleanWhitespace( cur );

}

cur = cur.nextSibling; // Move through the child nodes

}

}

?使用nodeType屬性.

Element (nodeType = 1):如li a input select等元素.

Text (nodeType = 3): 匹配文本元素

Document (nodeType = 9): This matches the root element of a document.

獲取元素內的文本內容

需要注意的是innertext在非mozilla瀏覽器中可以使用,火狐中無法使用.

Listing 5-15. Getting the Text Contents of the <strong> Element

// Non-Mozilla Browsers:

strongElem.innerText

// All platforms:

strongElem.firstChild.nodeValue

獲取元素內的html

? Mozilla-based browsers don’t return the <style> elements in an innerHTML statement.

? Internet Explorer returns its elements in all caps, which if you’re looking for consistency

can be frustrating.

? The innerHTML property is only consistently available as a property on elements of HTML DOM documents; trying to use it on XML DOM documents will result in retrieving null values.

獲取或設置一個元素的屬性值 getAttribute SetAttribute.

Jquery代碼學習

Jquery in action 選擇器部分學習

Ul li a 不管多少層次,會選中所有符合ul li 下的a.不管多少層級.

Ul li>a 只選擇直接孩子的a標簽.

Li:has(a)容器選擇器,選擇包含鏈接的li元素以進行某項操作.

通過位置進行定位的選擇器.

??

Jquery自定義的篩選選擇器:

?//防止重復提交的一個方法 w3c官方推薦的屬性設置 ????????????$("form").submit(function?()?{
$(":submit").attr("disabled",?"disabled");
}); ?

轉載于:https://www.cnblogs.com/huaxiaoyao/archive/2011/02/16/1956526.html

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