本来一直觉得这么基础的功能是没有什么好拿出来讲的,今天和网友聊天发现,由于缺乏对json的理解,很多人都还在继续带着自己的项目往ajax的方向进军,而完全不知道有一个好得多的替代品。所以写下这么个demo给大家参考:

< HTML >
< HEAD >
< title > 异步json例子 </ title >
< SCRIPT  LANGUAGE ="JavaScript" >
function  test(){
    
var  s  =  document.createElement( " SCRIPT " );
    document.getElementsByTagName(
" HEAD " )[ 0 ].appendChild(s);
    s.src
= " http://g2.qzone.qq.com/fcg-bin/cgi_emotion_list.fcg?uin=123456 " ;
}
function  visitCountCallBack(data){
    
for ( var  i  in  data){
        
var  e  = document.getElementById(i);
        
if (e) e.innerHTML = data[i];
    }

}
</ SCRIPT >
</ HEAD >
< BODY >
< button  onclick ="test()" > test </ button >< BR >
历史访问人数:
< span  id ="visitcount"  style ="color:#6600CC" > 点击test按钮获取数据 </ span >< BR >
今天访问人数:
< span  id ="dayvisit"  style ="color:#CC6633" > 点击test按钮获取数据 </ span >< BR >
阳光指数:
< span  id ="sun"  style ="color:red" > 点击test按钮获取数据 </ span >< BR >
爱心指数:
< span  id ="love"  style ="color:violet" > 点击test按钮获取数据 </ span >< BR >
雨露指数:
< span  id ="rain"  style ="color:blue" > 点击test按钮获取数据 </ span >< BR >
营养指数:
< span  id ="nutri"  style ="color:green" > 点击test按钮获取数据 </ span >< BR >
花匠级别:
< span  id ="gardener"  style ="color:#996633" > 点击test按钮获取数据 </ span >
</ BODY >
</ HTML >


这里请求的资源是
返回的是类似这样的一个js语句 :

visitCountCallBack({ " visitcount " : 1941 , " dayvisit " : 4 , " spacemark " : 0 , " markchange " : 0 , " sun " : 200 , " love " : 14 , " rain " : 200 , " nutri " : 200 , " level " : 4 , " gardener " : 11 });



科普一下:

相比xml,json的好处是:天生的跨浏览器(比如我的这个demo应该可以跨所有支持dhtml的浏览器而不需要任何修改),客户端解析代价(CPU和内存)非常小,非单根结构(xml是单根结构),标记名只出现一次(xml的标记名在大多数情况下都需要出现两次:<tag>...</tag>,因此浪费了很多流量)
主要缺点是只支持get方式请求,另外跨编码(json资源的编码和引用页面的编码不同)的时候要在script标签上指明charset(不像xml可以在<?xml>上指定)。

此外很多人并不知道json可以异步获取,这个例子很重要的一点是展示了如何异步获取json。  

GitHub 加速计划 / js / json
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5
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适用于现代 C++ 的 JSON。
最近提交(Master分支:4 个月前 )
f06604fc * :page_facing_up: bump the copyright years Signed-off-by: Niels Lohmann <mail@nlohmann.me> * :page_facing_up: bump the copyright years Signed-off-by: Niels Lohmann <mail@nlohmann.me> * :page_facing_up: bump the copyright years Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> Signed-off-by: Niels Lohmann <niels.lohmann@gmail.com> 23 天前
d23291ba * add a ci step for Json_Diagnostic_Positions Signed-off-by: Harinath Nampally <harinath922@gmail.com> * Update ci.cmake to address review comments Signed-off-by: Harinath Nampally <harinath922@gmail.com> * address review comment Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix typo in the comment Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix typos in ci.cmake Signed-off-by: Harinath Nampally <harinath922@gmail.com> * invoke the new ci step from ubuntu.yml Signed-off-by: Harinath Nampally <harinath922@gmail.com> * issue4561 - use diagnostic positions for exceptions Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci_test_documentation check Signed-off-by: Harinath Nampally <harinath922@gmail.com> * address review comments Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci check failures for unit-diagnostic-postions.cpp Signed-off-by: Harinath Nampally <harinath922@gmail.com> * improvements based on review comments Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix const correctness string Signed-off-by: Harinath Nampally <harinath922@gmail.com> * further refinements based on reviews Signed-off-by: Harinath Nampally <harinath922@gmail.com> * add one more test case for full coverage Signed-off-by: Harinath Nampally <harinath922@gmail.com> * ci check fix - add const Signed-off-by: Harinath Nampally <harinath922@gmail.com> * add unit tests for json_diagnostic_postions only Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci_test_diagnostics Signed-off-by: Harinath Nampally <harinath922@gmail.com> * fix ci_test_build_documentation check Signed-off-by: Harinath Nampally <harinath922@gmail.com> --------- Signed-off-by: Harinath Nampally <harinath922@gmail.com> 24 天前
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