js封装ajax

1 //调用方式：
2 ajax(    
3 　　'http://www.baidu.com',
4 　　{name:'json'}    
5 　　).then((res)=>{
6 　　　　console.log(res);
7 　　})

function ajax(url,data) {
    return new Promise((resolve,reject)=>{
        let xhr = new XMLHttpRequest();
        let temp = '?';
        for(let key in data){
            temp = temp + key + '=' + data[key] + '&';
        }
        temp = temp.substr(0, temp.length - 1); 
        xhr.open('get', url+temp);
        xhr.setRequestHeader("Content-type", 'application/x-www-form-urlencoded');
        xhr.onreadystatechange = function () {
    　　　　　if (xhr.readyState == 4 && xhr.status == 200) {
            resolve(xhr.responseText);
        }
    }
        xhr.send(temp);
    });
}

　　其中：

 1 //(如果需要设置特殊的表单提交方式)则修改
 2 xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
 3 //application/x-www-form-urlencoded -> 
 4 let data = "name=json";
 5 
 6 //application/json -> 
 7 let data = JSON.stringify({name:'json'});
 8 
 9 //multipart/form-data -> 
10 let data = new FormData();
11 data.append('name','json');