处理超时Ajax之五

上一篇只是检查是否超时，超时后却不做任何处理。这里如果超时，会给failure第二个参数msg赋值为“request timeout”。

这样使用者能清楚的知道一次HTTP请求的细节。实现细节较为诡异，慢慢体会。这里timeout的效果和JQuery，Ext是一样的。如下

Ajax.text('../servlet/Ajax',{
	timeout : 2000,
	success : function(result){},
	failure : function(xhr,msg){
		alert(msg);
	}
});

完整源码

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'){
			data = _serialize(data);
		}
		if(method == 'GET' && data){
			url += (url.indexOf('?') == -1 ? '?' : '&') + data;
			data = null;
		}	
		var xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
		if(!xhr){return;}
		var isTimeout = false, timer;
		if(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':
					result = function(str){
						return (new Function('return ' + str))();
					}(xhr.responseText);
					break;
				case 'xml':
					result = xhr.responseXML;
					break;
			}
			success(result);
		}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;
	})();
}();