改造请求参数Ajax之二

接上篇。引入了一个私有函数_serialize，它会把js对象串行化成HTTP所需参数模式，接受如下两种结构

{name:'jack',age:20} --> name=jack&age=20
{fruit:['apple','banana','orange']} --> fruit=apple&fruit=banana&fruit=orange

请求后台的一个servlet，发送参数name=jack,age=20，默认使用异步，GET方式。现在data可以如下了

Ajax.request('servlet/ServletJSON',{
		data : {name:'jack',age:20},
		success : function(xhr){
			//to do with xhr
		},
		failure : function(xhr){
			//to do with xhr
		}
	}
);

完整代码

Ajax = 
function(){
	function request(url,opt){
		function fn(){}
		var async   = opt.async !== false,
			method  = opt.method 	|| 'GET',
			encode  = opt.encode 	|| 'UTF-8',
			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 = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
		xhr.onreadystatechange = function(){
			_onStateChange(xhr,success,failure);
		};
		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,success,failure){
		if(xhr.readyState == 4){
			var s = xhr.status;
			if(s>= 200 && s < 300){
				success(xhr);
			}else{
				failure(xhr);
			}
		}else{}
	}
	return {request:request};
}();

这里仅仅是使data可以是对象类型，貌似没啥大用。但如果与表单(form)结合的话还是很有用的。当我们使用form但又想用Ajax方式提交，那么把form中元素序列化成HTTP请求的参数类型是一个费劲的活。这里写个工具函数formToHash，将form元素按键值形式转换成对象返回

function formToHash(form){
	var hash = {}, el;
	for(var i = 0,len = form.elements.length;i < len;i++){
		el = form.elements[i];
		if(el.name == "" || el.disabled) continue;
		switch(el.tagName.toLowerCase()){
		case "fieldset":
			break;
		case "input":
			switch(el.type.toLowerCase()){
			case "radio":
				if(el.checked)
					hash[el.name] = el.value;
				break;
			case "checkbox":
				if(el.checked){
					if(!hash[el.name]){
						hash[el.name] = [el.value];
					}else{
						hash[el.name].push(el.value);
					}
				}
				break;
			case "button":
				break;
			case "image":
				break;
			default:
				hash[el.name] = el.value;
				break;
			}
			break;
		case "select":
			if(el.multiple){
				for(var j = 0, lens = el.options.length;j < lens; j++){
					if(el.options[j].selected){
						if(!hash[el.name]){
							hash[el.name] = [el.options[j].value];
						}else{
							hash[el.name].push(el.options[j].value);
						}
					}
				}
			}else{
				hash[el.name] = el.value;
			}
			break;
		default:
			hash[el.name] = el.value;
			break;
		}
	}
	form = el = null;
	return hash;
}

相关：

ajax_02.zip

https://github.com/snandy/io