Convert parameters into formdata in js and send to the backend

let formData = new FormData(),
let list = [{'name':"csdn"},{'age',18}]
params = {
    userId: "111111111",
    userInfo:list ,
    userName: "csdn",
};
this._.forIn(params, (value, key) => {
    if (value) {
        formData.append(key, value);
    }
});
//  如果这么传值后端会报错  userInfo传的值为[object object] 
//  正确方法：对象的类型转换成字符串类型
```````````
     userInfo:JSON.stringify(list) ,
```````````