跨域之jsonp

简介:

先创建一个html文件,代码如下:

1 <body>2    <p>名字:<span id="name"></span></p>3 <script>4   function test(obj) {5    document.getElementById("name").innerHTML = obj.name;6   }7 </script>8 </body>

此时在浏览器打开这个文件,页面中只有“名字:”这三个字符。

现在创建一个JS文件,test.js,其中的代码如下:

1 var person = {2     name: "Jack",3     age: 204 }5 test(person);

通过<script>标签在html文件中引入这个test.js文件(添加到body结束标签之前):

1 <script src="test.js"></script>

再在浏览器中打开html文件就会看到:

如果把这个test.js放在百度的服务器上,在淘宝的页面上有一个test函数声明,然后动态地创建一个<script>标签来引用这个test.js,那么在淘宝的页面上就可以显示来自百度的服务器的数据,这就是jsonp的原理。当然引用的不一定非要是js文件,也可以是php、.net等文件,只要在这些文件中事先写好相应的代码即可。

下面用聚合数据的天气预报接口和新浪的城市查询接口为例来介绍jsonp。

首先是新浪的城市查询接口。

新浪的城市查询接口是:

http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=js

可以直接在浏览器中打开,发现是一个名为remote_ip_info的Javascript对象,

var remote_ip_info = {    "ret":1,    "start":-1,    "end":-1,    "country":"\u4e2d\u56fd",    "province":"\u6cb3\u5357",    "city":"\u8bb8\u660c",    "district":"",    "isp":"",    "type":"",    "desc":""};

那么在本地的测试页面中可以使用这个接口获取所在的城市,代码如下:

 1 //获取当前城市 2     function getCity(url) { 3       var city = ''; 4       //创建一个script标签 5       var script = document.createElement("script"); 6       //设置script标签引用的url 7       script.setAttribute("src",url); 8       //将script标签添加到头部,也可以添加到其他地方 9       var head = document.getElementsByTagName('head')[0];10       head.appendChild(script);11       //如果script标签加载完成,获取城市12       script.onload = function() {//script.onload不兼容IE8及以下版本13          city = remote_ip_info["city"];14          console.log(city);15       };16 17       //移除创建的script标签18       head.removeChild(script);19     }20 21     //该URL是新浪的获取当前城市的API,采用jasop方法获取数据22     getCity("http://int.dpool.sina.com.cn/iplookup/iplookup.php?format=js");

下面是聚合数据的天气预报接口。

接口示例:http://op.juhe.cn/onebox/weather/query?cityname=%E6%B8%A9%E5%B7%9E&key=您申请的KEY

使用这个接口时至少要传入三个参数:

  1. cityname是要查询的城市名,可以用前面新浪的城市查询接口得到的数据。

  2. key是申请使用聚合数据天气预报接口时,给的APPKey。

  3. 另外还有一个callback参数,传入一个函数名,服务器会把查询后得到的数据拼接成函数调用的形式返回来,比如传入test函数名,则返回来test({"date":"2011-11-11","wind":"微风"}),所以要在测试页面声明好这个函数,以便对返回来的数据进行处理。

下面是代码:

html代码,将获得数据在页面中显示出来

1 <p id="chuanyi"></p>2 <p id="yundong"></p>3 <p id="ziwaixian"></p>

获得天气情况数据的代码,原理与获取当前城市的原理一样,不同的是要事先指定回调函数,并将函数名加到url的末尾。

 1 function $(id) { 2       return document.getElementById(id); 3 } 4  5 //指定回调函数 6     function callback(data) { 7      $("chuanyi").innerHTML = "穿衣指数:" + data.result.data.life.info.chuanyi; 8      $("yundong").innerHTML = "运动指数:" + data.result.data.life.info.yundong; 9      $("ziwaixian").innerHTML = "紫外线:" + data.result.data.life.info.ziwaixian;10     }11 12     function getWeather(city) {13       var url = 'http://op.juhe.cn/onebox/weather/query?cityname='+encodeURIComponent(city)+'&key=abbac0fc4fccbec34891de77bb1cfb4e&callback=callback';//该URL是聚合数据的天气预报API,采用jasop方法获取数据14       console.log(encodeURIComponent(city));15       var script = document.createElement("script");16       script.setAttribute("src",url);17       var head = document.getElementsByTagName('head')[0];18       head.appendChild(script);19       head.removeChild(script);20     }

有了以上代码,还不能获取到天气数据,因为getWeather()函数还没有调用。为了能将获取到的城市数据传给getWeather()函数,要在getCity()函数内部script的onload事件处理程序中调用getWeather()函数。

下面是调用getWeather函数返回的数据,一大串:

  1 callback({  2     "reason":"successed!",  3     "result":{  4         "data":{  5             "pubdate":"2016-11-11",  6             "pubtime":"11:00:00",  7             "realtime":{  8                 "city_code":"101180401",  9                 "city_name":"许昌", 10                 "date":"2016-11-11", 11                 "time":"16:00:00", 12                 "week":5, 13                 "moon":"十月十二", 14                 "dataUptime":1478853365, 15                 "weather":{ 16                     "temperature":"15", 17                     "humidity":"64", 18                     "info":"多云", 19                     "img":"1" 20                 }, 21                 "wind":{ 22                     "direct":"南风", 23                     "power":"3级", 24                     "offset":null, 25                     "windspeed":null 26                 } 27             }, 28             "life":{ 29                 "date":"2016-11-11", 30                 "info":{ 31                     "chuanyi":["较冷","建议着厚外套加毛衣等服装。年老体弱者宜着大衣、呢外套加羊毛衫。"], 32                     "ganmao":["较易发","天凉,昼夜温差较大,较易发生感冒,请适当增减衣服,体质较弱的朋友请注意适当防护。"], 33                     "kongtiao":["较少开启","您将感到很舒适,一般不需要开启空调。"], 34                     "xiche":["较适宜","较适宜洗车,未来一天无雨,风力较小,擦洗一新的汽车至少能保持一天。"], 35                     "yundong":["较适宜","天气较好,但考虑气温较低,推荐您进行室内运动,若户外适当增减衣物并注意防晒。"], 36                     "ziwaixian":["弱","紫外线强度较弱,建议出门前涂擦SPF在12-15之间、PA+的防晒护肤品。"] 37                 } 38             }, 39             "weather":[ 40                 { 41                     "date":"2016-11-11", 42                     "info":{ 43                         "day":["1","多云","17","","微风","06:53"], 44                         "night":["0","晴","7","","微风","17:23"] 45                     }, 46                     "week":"五", 47                     "nongli":"十月十二" 48                 }, 49                 { 50                     "date":"2016-11-12", 51                     "info":{ 52                         "dawn":["0","晴","7","无持续风向","微风","17:23"], 53                         "day":["0","晴","17","","微风","06:54"], 54                         "night":["1","多云","8","","微风","17:23"] 55                     }, 56                     "week":"六", 57                     "nongli":"十月十三" 58                 }, 59                 { 60                     "date":"2016-11-13", 61                     "info":{ 62                         "dawn":["1","多云","8","无持续风向","微风","17:23"], 63                         "day":["1","多云","17","","微风","06:55"], 64                         "night":["0","晴","9","","微风","17:22"] 65                     }, 66                     "week":"日", 67                     "nongli":"十月十四" 68                 }, 69                 { 70                     "date":"2016-11-14", 71                     "info":{ 72                         "dawn":["0","晴","9","无持续风向","微风","17:22"], 73                         "day":["1","多云","17","","微风","06:56"], 74                         "night":["2","阴","5","","微风","17:21"] 75                     }, 76                     "week":"一", 77                     "nongli":"十月十五" 78                 }, 79                 { 80                     "date":"2016-11-15", 81                     "info":{ 82                         "dawn":["2","阴","5","无持续风向","微风","17:21"], 83                         "day":["1","多云","13","","微风","06:57"], 84                         "night":["1","多云","6","","微风","17:21"] 85                     }, 86                     "week":"二", 87                     "nongli":"十月十六" 88                 } 89             ], 90             "f3h":{ 91                 "temperature":[ 92                     { 93                         "jg":"20161111170000", 94                         "jb":"15" 95                     }, 96                     { 97                         "jg":"20161111200000", 98                         "jb":"13" 99                     },100                     {101                         "jg":"20161111230000",102                         "jb":"10"103                     },104                     {105                         "jg":"20161112020000",106                         "jb":"10"107                     },108                     {109                         "jg":"20161112050000",110                         "jb":"8"111                     },112                     {113                         "jg":"20161112080000",114                         "jb":"7"115                     },116                     {117                         "jg":"20161112110000",118                         "jb":"14"119                     },120                     {121                         "jg":"20161112140000",122                         "jb":"16"123                     },124                     {125                         "jg":"20161112170000",126                         "jb":"14"127                     }128                 ],129                 "precipitation":[130                     {"jg":"20161111170000","jf":"0"},131                     {"jg":"20161111200000","jf":"0"},132                     {"jg":"20161111230000","jf":"0"},133                     {"jg":"20161112020000","jf":"0"},134                     {"jg":"20161112050000","jf":"0"},135                     {"jg":"20161112080000","jf":"0"},136                     {"jg":"20161112110000","jf":"0"},137                     {"jg":"20161112140000","jf":"0"},138                     {"jg":"20161112170000","jf":"0"}139                 ]140             },141             "pm25":{142                 "key":"Xuchang",143                 "show_desc":0,144                 "pm25":{145                     "curPm":"50",146                     "pm25":"25",147                     "pm10":"51",148                     "level":1,149                     "quality":"优",150                     "des":"可正常活动。"151                 },152                 "dateTime":"2016年11月11日16时",153                 "cityName":"许昌"154             },155             "jingqu":"",156             "jingqutq":"",157             "date":"",158             "isForeign":"0"159         }160     },161     "error_code":0162 })



本文转自zsdnr 51CTO博客,原文链接:http://blog.51cto.com/12942149/1928949,如需转载请自行联系原作者








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