react axios 发送post请求的时候字符串 “null” 如何修改为 null ？

Question

这个是一个编辑页面

json 数据

{
  "id": 1,
  "username": "monic_lope",
  "firstname": "Moni",
  "lastname": null,
  "description": "\u00abMemoria selectiva ",
  "avatar": "5e5183e40e548.jpg",
  "email": "sweetmg@gmail.com",
  "account_id": "143914624",
  "followers": 12560,
  "posts": 6589,
  "following": 12560,
  "rate": "13.50",
  "grade": null,
  "affiliate": null,
  "avg_likes": 1384,
  "avg_comments": 29,
  "phone": null,
  "status": "success",
  "web": null,
  "facebook": null,
  "youtube": null,
  "address": null,
  "city": null,
  "postal_code": null,
  "region": null,
  "fee": null,
  "created_at": "2020-02-06T18:47:20.000000Z",
  "updated_at": "2021-04-22T13:47:06.000000Z",
}

import React, {useState, useMemo, useEffect} from 'react';
import {Layout, Page, Stack, Badge, PageActions} from '@shopify/polaris';
import axios from 'axios';


const InfluencersEdit = (props: any) => {
    const [item, setItem] = useState({
        id: '',
        username: '',
        firstname: '',
        lastname: '',
        email: '',
        phone: '',
        tags: '',
        followers: '',
        posts: '',
        following: '',
        rate: '',
        description: '',
        address: '',
        city: '',
        region: '',
        postal_code: '',
        facebook: '',
        youtube: '',
        status: '',
        avg_comments: '',
        avg_likes: '',
    });
    
   useEffect(() => {
        axios.get('/api/influencers/' + influencer).then(res => {
            setItem(res.data); 
        });
    }, []);
    
    const handleinfluencersUpload = () => {
        let formData = new FormData();
        //@ts-ignore
        formData.append('file', file);
        formData.append('username', item.username);
        formData.append('firstname', item.firstname);
        formData.append('lastname', item.lastname);
        formData.append('email', item.email);
        formData.append('phone', item.phone);
        formData.append('followers', item.followers);
        formData.append('posts', item.posts);
        formData.append('following', item.following);
        formData.append('rate', item.rate);
        formData.append('description', item.description);
        formData.append('address', item.address);
        formData.append('city', item.city);
        formData.append('region', item.region);
        formData.append('postal_code', item.postal_code);
        formData.append('facebook', item.facebook);
        formData.append('youtube', item.youtube);
        formData.append('status', item.status);
        formData.append('tags', selectedOptions.join(', '));
        formData.append('_method', 'put');

        axios
            .post(`/api/influencers/${item.id}`, formData)
            .then(res => {})
            .catch(error => {});
    };
    
    

}

//采用了shopify polaris的 TextField

                        <div className="_2iE3d">
                            <TextContainer spacing="tight">
                                <TextField
                                    label="粉丝互动率"
                                    type="number"
                                    value={item.followers.toString()}
                                    onChange={value => {
                                        setItem({
                                            ...item,
                                            followers: value,
                                        });
                                    }}
                                />
                            </TextContainer>
                        </div>

请求：

响应

Answer 1

但是你 tags 里面是 null 呀。你看看你那个写的和别的有什么不同。

因为你这个走的 form-data, null 这个概念是 json 的，所以你走 application/json 才可以。

或者你判断一下，如果没有值就别 append 了。undefined 和 null 都一样。