1.1.1 摘要
现在，许多网站都提供在线图片和图书阅读的功能，这种方式比下载后阅读来的直观和人性化，要实现该功能涉及到点击处理和图片动态加载。
在接下来的博文中，我们将通过Javascript方式实现在线阅读这一功能。
1.1.2 正文
Index页面
首先，我们创建index.html页面，它包含三个div元素分别是content、controls和doccontainer，其中controls用来显示翻页控件（前/后翻），而doccontainer用于显示图片，具体定义如下：
<!doctype html>
<html lang="en-US">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8">
<title>Online Document Viewer Demo</title>
<meta name="author" content="JK_Rush">
<link rel="stylesheet" type="text/css" media="all" href="css/style.css">
<script type="text/javascript" src="js/jquery-1.9.1.min.js"></script>
<script type="text/javascript" src="js/jquery.onlinedocview.js"></script>
<script type="text/javascript">
$(document).ready(function () {
$("#controls").viewer();
});
</script>
</head>
<body>
<div>
<div id="Div1">
<h1>Online Document Viewer Demo</h1>
<div id="controls">
<div id="backpage" class="ios-arrow-left">Back</div>
<div id="forwardpage" class="ios-arrow-right">Forward</div>
</div>
<div id="doccontainer">
<img src="img/1.jpg" data-page="1" title="click for next page"></div>
</div><!-- END #content -->
</div><!-- END # -->
</body>
图1 index页面
上面，我们定义了index.html页面，引用了jQuery库文件，在controls元素中包含backpage和forwardpage控件元素，它用于表示前或后翻页的操作；而doccontainer中img的元素用于显示文档，每当用户点击前或后翻页就会加载相应的内容到img元素中。
Javascript
接下来，我们需要实现在线文档的翻页功能和内容的动态加载，我们定义jQuery插件方法viewer()，当用户点击#backpage和#forwardpage控件元素时实现向前或后翻页并且动态地加载相应的文档，具体定义如下：
/*****
* The viewer function, when user click #forwardpage, #backpage or image directly,
* load the corrosponding image.
******/
$.fn.viewer = function(options) {
'use strict'; var opts = $.extend(true, {}, $.fn.viewer.defaults, options); var $docImage = $('#doccontainer > img'); // Implements the image click function.
$docImage.on('click', function(e) {
e.preventDefault();
var currentId = $(this).attr('data-page'),
// Gets next page id.
nextImgId = parseInt(currentId) + 1,
nextImgSrc = opts.imgDirectory; if (currentId == opts.lastDocNum) {
// If the last page, then do nothing
return false;
} nextImgSrc += getFile(nextImgId);
$(this).attr('data-page', nextImgId);
$(this).attr('src', nextImgSrc);
}) // Implements #forwardpage and #backpage control click function.
$('#controls > #forwardpage, #controls > #backpage').on('click', function(e) {
e.preventDefault(); var currentId = $docImage.attr('data-page'),
nextImgSrc = opts.imgDirectory; if ($(this).attr('id') == 'backpage') {
var nextImgId = parseInt(currentId) - 1;
} else if ($(this).attr('id') == 'forwardpage') {
var nextImgId = parseInt(currentId) + 1;
} if ((currentId == opts.lastDocNum && $(this).attr('id') == 'forwardPage') ||
(currentId == 1 && $(this).attr('id') == 'backpage')) {
// If the last page or the first page, then do nothing.
return false;
} // Loads corresponding image file.
nextImgSrc += getFile(nextImgId);
$docImage.attr('data-page', nextImgId);
$docImage.attr('src', nextImgSrc); }) // Constructs the image file name.
function getFile(n) {
return n + '.' + opts.fileType;
} };
上面，我们定义了jQuery方法viewer()，我们实现了#forwardpage、#backpage和#doccontainer的点击事件处理方法，当用户点击#forwardpage、#backpage或#doccontainer动态地加载相应的文档，我们通过修改img元素的src属性来动态加载文档，并且通过data-page属性保存当前文档的页码。
CSS样式
最后，我们给#forwardpage和#backpage控件元素添加CSS样式，具体化定义如下：
/*Back and Forward button style*/
.ios-arrow-left {
cursor:pointer;
display : block;
position:absolute;
z-index : 0;
left:50px;
top:50px;
height:30px;
width:auto;
padding: 0 10px 0 6px;
background-repeat:repeat-x;
background-size : 100% 30px;
background-position :0;
background-image : -webkit-linear-gradient(
bottom,
rgba(0,0,0,0) 0%,
rgba(0,0,0,0) 50%,
rgba(255,255,255,0.1) 50%,
rgba(255,255,255,0.3) 100%
);
border-radius: 5px;
border-bottom: 1px solid rgba(255,255,255,0.4);
box-shadow :0 -1px 1px rgba(0,0,0,0.2)inset,
0 1px 2px rgba(0,0,0,0.8)inset;
font-family : HelveticaNeue;
font-weight: 400;
font-size : 12px;
line-height : 30px;
text-align:center;
color:#fff;
text-shadow : 0px -1px 0px rgba(0,0,0,0.8);
}
.ios-arrow-left:before{
position:absolute;
content : ' ';
left:-8px;
top:3.5px;
height : 24px;
width: 24px;
z-index : 1;
background-repeat:repeat-x;
background-size : 20px 20px;
background-position :-1px -0.5px;
background-image :
-webkit-gradient(linear, left bottom, right top,
from(rgba(0,0,0,0)),
color-stop(0.5, rgba(0,0,0,0)),
color-stop(0.5, rgba(255,255,255,0.1)),
to(rgba(255,255,255,0.3)));
-webkit-transform : rotate(-45deg) skew(-10deg, -10deg);
border-top-right-radius : 10px;
border-top-left-radius :0px;
border-bottom-right-radius : 0px;
border-bottom-left-radius : 10px;
border-left : 1.5px solid rgba(255,255,255,0.4);
box-shadow : 1px 1px 1px rgba(0,0,0,0.4) inset,
-1px 1px 1px rgba(0,0,0,0.5) inset;
-webkit-mask-image :
-webkit-gradient(linear, left top, right bottom,
from(#000000),
color-stop(0.4,#000000),
color-stop(0.5, transparent),
to(transparent));
} .ios-arrow-right {
cursor:pointer;
display : block;
position:absolute;
z-index : 0;
right:50px;
top:50px;
height:30px;
width:auto;
padding: 0 6px 0 10px;
background-repeat:repeat-x;
background-size : 100% 30px;
background-position :0;
background-image : -webkit-linear-gradient(
bottom,
rgba(0,0,0,0) 0%,
rgba(0,0,0,0) 50%,
rgba(255,255,255,0.1) 50%,
rgba(255,255,255,0.3) 100%
);
border-radius: 5px;
border-bottom: 1px solid rgba(255,255,255,0.4);
box-shadow :0 -1px 1px rgba(0,0,0,0.2)inset,
0 1px 2px rgba(0,0,0,0.8)inset;
font-family : HelveticaNeue;
font-weight: 400;
font-size : 12px;
line-height : 30px;
text-align:center;
color:#fff;
text-shadow : 0px -1px 0px rgba(0,0,0,0.8);
}
.ios-arrow-right:after{
position:absolute;
content : ' ';
right:-7.5px;
top:3px;
height : 24px;
width: 24px;
z-index : 1;
background-repeat:repeat-x;
background-size : 20px 20px;
background-position :-1px -0.5px;
background-image :
-webkit-gradient(linear, left bottom, right top,
from(rgba(255,255,255,0.3)),
color-stop(0.5, rgba(255,255,255,0.1)),
color-stop(0.5, rgba(0,0,0,0)),
to(rgba(0,0,0,0)));
-webkit-transform : rotate(135deg) skew(-10deg, -10deg);
border-top-right-radius : 10px;
border-top-left-radius :0px;
border-bottom-right-radius : 0px;
border-bottom-left-radius : 10px;
border-top : 1.5px solid rgba(255,255,255,0.4);
box-shadow : 1px 1px 1px rgba(0,0,0,0.5) inset,
-1px 1px 1px rgba(0,0,0,0.4) inset;
-webkit-mask-image :
-webkit-gradient(linear, left top, right bottom,
from(#000000),
color-stop(0.4,#000000),
color-stop(0.5, transparent),
to(transparent));
} .ios-arrow-right,
.ios-arrow-right:after,
.ios-arrow-left,
.ios-arrow-left:before {
background-color: rgba(33,33,33,1);/*normalcolor*/
} .ios-arrow-right:hover,
.ios-arrow-right:hover:after,
.ios-arrow-left:hover,
.ios-arrow-left:hover:before {
background-color: rgba(0,0,0,1);/*hovercolor*/
} /*************************************************
图2在线文档
现在，我们已经实现了在线查看文档的功能了，由于我们使用Javascript动态地加载文档内容，所以无需刷新页面，我们只需替换相应的文档链接地址就好了，这样不但减少了Http请求的次数减轻了网站的负载，而且无刷新用户体验更好。
1.1.3 总结
本文我们通过一个在线文档查看程序，介绍了通过jQuery实现动态加载数据的功能，通过使用jQuery动态加载数据无需刷新页面，只需替换相应的文档链接地址就好了，并且减少了网站的Http请求次数，减轻网络负载和加载延迟。
参考
[1] http://designshack.net/articles/javascript/coding-an-ajax-style-paged-document-viewer-with-jquery/