### Ajax封装
```javascript
function ajxa(){
var xhr = null
//浏览器兼容
var params = formasParams(options.data)
if(window.XMLHttpRequest()){
xhr = new XMLHttpRequest()
}else{
xhr = new ActiveXObject('Microsoft.XMLHttpRequest')
}
//type请求连接
if(options.type == 'GET'){//注意类型为大写
xhr.open(options.type,options.url + "?" + params,options.async)
xhr.send(null)
}else if(options.type == 'POST'){
xhr.open(options.type,options.url,options.async);
xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xhr.send(params);
}
xhr.onreadystatechange = function(){
if(xhr.readystatechange == 4 && xhr.status == 200){
options.success(xhr.responseText);
}
}
function formsParms(data){
var arr = []
for(var prop in data){
arr.push(prop + '=' + data[prop]);
}
return arr.join('&')
}
}
axja({
url: 'http:www.amistyz.com:5555/login',
type: 'post',
async: true,
data: {
username: '123421',
password: 'sadasd'
},
success: function(data){
console.log(data)
}
})
```
