新API解析JSON-Ajax之七

这是Ajax系列的最后一篇。

ECMAScript 5发布有段时间了，其中就包括了解析JSON的原生API-JSON.parse。许多浏览器已经支持了。主流JS库如JQuery，Ext，Prototype都优先使用JSON.parse，不支持该方法的浏览器则使用new Function或eval。 为何优先使用JSON.parse，我想一个就是性能，原生的总是要快一些吧。此外JSON.parse较eval也更安全。

这里也当然不能落后了，优先使用JSON.parse，不行再用new Function方式。最后失败了会给failure的第二个参数msg赋值为"parse json error"

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result = function(str){     try{         return JSON.parse(str);     }catch(e){         try{             return (new Function('return ' + str))();         }catch(e){             failure(xhr,'parse json error',e);         }     } }(xhr.responseText);

 

完整源码

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Ajax = function(){     function request(url,opt){         function fn(){}         opt = opt || {};         var async   = opt.async !== false,             method  = opt.method    || 'GET',             type    = opt.type      || 'text',             encode  = opt.encode    || 'UTF-8',             timeout = opt.timeout   || 0,             data    = opt.data      || null,             success = opt.success   || fn,             failure = opt.failure   || fn;             method  = method.toUpperCase();         if(data && typeof data == 'object'){//对象转换成字符串键值对             data = _serialize(data);         }         if(method == 'GET' && data){             url += (url.indexOf('?') == -1 ? '?' : '&') + data;             data = null;         }           var xhr = function(){             try{                 return new XMLHttpRequest();             }catch(e){                 try{                     return new ActiveXObject('Msxml2.XMLHTTP');                 }catch(e){                     try{                         return new ActiveXObject('Microsoft.XMLHTTP');                     }catch(e){                         failure(null,'create xhr failed',e);                     }                 }             }         }();         if(!xhr){return;}         var isTimeout = false, timer;         if(async && timeout>0){             timer = setTimeout(function(){                 xhr.abort();                 isTimeout = true;             },timeout);         }         xhr.onreadystatechange = function(){             if (xhr.readyState == 4 && !isTimeout){                 _onStateChange(xhr, type, success, failure);                 clearTimeout(timer);             }else{}         };         xhr.open(method,url,async);         if(method == 'POST'){             xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded;charset=' + encode);         }         xhr.send(data);         return xhr;     }     function _serialize(obj){         var a = [];         for(var k in obj){             var val = obj[k];             if(val.constructor == Array){                 for(var i=0,len=val.length;i<len;i++){                     a.push(k + '=' + encodeURIComponent(val[i]));                 }                           }else{                 a.push(k + '=' + encodeURIComponent(val));             }                       }         return a.join('&');     }     function _onStateChange(xhr,type,success,failure){         var s = xhr.status, result;         if(s>= 200 && s < 300){             switch(type){                 case 'text':                     result = xhr.responseText;                     break;                 case 'json':                     // http://snandy.javaeye.com/blog/615216                     result = function(str){                         try{                             return JSON.parse(str);                         }catch(e){                             try{                                 return (new Function('return ' + str))();                             }catch(e){                                 failure(xhr,'parse json error',e);                             }                         }                     }(xhr.responseText);                 break;                 case 'xml':                     result = xhr.responseXML;                     break;             }             // text, 返回空字符时执行success             // json, 返回空对象{}时执行suceess，但解析json失败，函数没有返回值时默认返回undefined             typeof result !== 'undefined' && success(result);                           //请求超时，调用abort后xhr.status为0，但不知为0时是否还有其它的情况         }else if(s===0){             failure(xhr,'request timeout');         }else{             failure(xhr,xhr.status);         }         xhr = null;     }     return (function(){         var Ajax = {request:request}, types = ['text','json','xml'];         for(var i=0,len=types.length;i<len;i++){             Ajax[types[i]] = function(i){                 return function(url,opt){                     opt = opt || {};                     opt.type = types[i];                     return request(url,opt);                 }             }(i);         }         return Ajax;     })(); }();

 

相关：

ajax_07.zip

https://github.com/snandy/io