实现效果图

image

功能预览

【less】上传文件的input框样式的改造
获取图片列表
点击上传图片 + 转换成base64
上传中loading
上传失败
删除图片
查看大图
下载图片 + Blob URL
useState 与 useEffect的使用
跨域
静态文件的查看
查询/删除/添加文件
uuid
用同步的方式书写异步的操作（封装 async await promise集合体）
axios

【前端】React

1.【less】上传文件的input框样式的改造


    
    Upload
    handleUploadImage(props)}/>

主要用到的是原生的input框：
type="file"弹出选择上传文件的框；
accept="image/*"来限制你选择上传的文件只能是图片类型的；
当你弹出选择文件的框之后，无论是选择还是取消都会触发onChange事件。

原生input上传文件的样式很丑，于是换样式成了重中之重！

思路：
1.把input框给隐藏掉
2.并且要设置一个与最终样式同样大小的宽高，通过子绝父相让input框覆盖在最上层，这样才能够命中点击事件

.upload-container{
    margin: 5px;
    padding: 3px;
    float: left;
    border-style: dashed;
    background-color: #f5f5f5;
    position: relative; //父相
    flex-direction: column;

    .icon{
      color: #e1e1e1;
      margin-top: 10px;
      font-size: 40px;
      font-weight: bolder;
    }
    .name{
      color: #a3a3a3;
    }
    input{
      width: 100%;
      height: 100%; // 与父样式等宽高
      cursor: pointer;
      position: absolute; // 子绝
      top: 0;
      opacity: 0; // 全透明
    }
  }

2. 用同步的方式书写异步的操作（封装 async await promise集合体）+ 获取图片列表 + useState

const baseUrl = 'http://localhost:8080/image';

const getImageListUrl = `${baseUrl}/list`;

const [list, setList] = useState([]);

const ajax = (url, data={}, type='GET') =>{
    return new Promise((resolve)=>{
        const promise = type === 'GET' ? axios.get(url, {params: data}) : axios.post(url, data)
        promise.then(res=>{
            const data = res.data;
            data.status !== 0 ? message.error(data.msg) : resolve(data);
        }).catch(err => {
            message.error('Network request Error: '+err);
        })
    })
};

const getAndUpdateImageList = async(setList) => {
    const data = await ajax(getImageListUrl);
    setList(data.data);
};

3. 点击上传图片 + 转换成base

出现上传文件的框，无论是选择还是取消，都会触发onChange事件，所以要判断你选择的targetFile是否存在。

通过FileReder将图片转成base64，用同步的方式将最终结果抛出去:

const getBase64 = (file) => {
    const fileReader = new FileReader();
    fileReader.readAsDataURL(file);
    return new Promise((resolve)=>{
        fileReader.onload = (data) => {
            resolve(data.target.result)
        }
    })
};

获取到了base64之后再发送axios请求到后端：

const handleUploadImage= async ({list,action,uploadImage,setUploadLoading, setUploadErrorFileName})=>{
    const input = document.getElementById('upload-image');
    const targetFile = input.files[0];
    if (targetFile){
        setUploadLoading(true);
        const { name } = targetFile;
        const imageBase64 = await getBase64(targetFile);
        await axios.post(action, {imageBase64, name})
            .then(()=>{
                uploadImage(action + "/" + name);
            }).catch(() => {
                setUploadErrorFileName(name);
            });
        setUploadLoading(false);
    }
};

4. 上传中loading

当我们开始上传图片的时候，会将uploadLoading设置成true，上传成功之后会将uploadLoading再设置成false！

const handleUploadImage= async ({list,action,uploadImage,setUploadLoading, setUploadErrorFileName})=>{
    const input = document.getElementById('upload-image');
    const targetFile = input.files[0];
    if (targetFile){
        setUploadLoading(true);
        ...
        setUploadLoading(false);
    }
};

const [uploadLoading, setUploadLoading] = useState(false);

{uploadLoading && renderUploading()}

const renderUploading =()=> (
    
        
        Uploading...
    
);

5. 上传失败

与loading其实同理, 其次，上传失败之后设置uploadErrorFileName来渲染失败的样式。

await axios.post(action, {imageBase64, name})
            .then(()=>{
                ...
            }).catch(() => {
                setUploadErrorFileName(name);
            });

const [uploadErrorFileName, setUploadErrorFileName] = useState(null);

{uploadErrorFileName && renderUploadError(uploadErrorFileName,setUploadErrorFileName)}

const renderUploadError =(uploadErrorFileName, setUploadErrorFileName)=> (
    
        
        Error!
        {uploadErrorFileName}
        
             setUploadErrorFileName(null)}/>
        
    
);

6. 删除图片

const deleteImage = async ({name}, setList)=>{
    await ajax(deleteImageUrl,{name});
    getAndUpdateImageList(setList);
};

7. 查看大图

用到了Antd的上传图片一样，用到的Modal框去显示大图，用previewSrc保存选择的结果

const [previewSrc, setPreviewSrc] = useState(null);

 setPreviewSrc(null)} >

8. 下载图片 + blob

思路：
1.用a标签的download属性来实现下载效果，因为下载按钮是Icon，所以点击download Icon之后触发a标签的download

2.使用Blob: 使用URL.createObjectURL()函数可以创建一个Blob URL

downloadImage(item, onDownload)}/>

const downloadImage=(item, onDownload)=>{
    const target = document.getElementById('download-image');
    const blob = new Blob([item.src]);
    target.href = URL.createObjectURL(blob);
    target.click();
    onDownload(item);
};

【后端】Nest

1.跨域

app.enableCors();

2.静态文件暴露

const app = await NestFactory.create(AppModule);
  app.useStaticAssets(join(__dirname, '..', 'data/images'), {
    prefix: '/images/',
  });

3.写文件

解析base64,生成buffer

fs.writeFile(buffer)

@Post('/image/add')
  getImage(@Req() req, @Res() res): void {
    const {imageBase64, name} = req.body;
    const base64Data = imageBase64.replace(/^data:image\/\w+;base64,/, '');
    const dataBuffer = new Buffer(base64Data, 'base64');
    fs.writeFile(`data/images/${name}`, dataBuffer, (err) => {
      if (err) {
        res.send(err);
      } else {
        res.send({status: 0 });
      }
    });
  }

4.读文件

fs.readdirSync(文件名)

@Get('/image/list')
  getProductList(@Res() res): void {
    const data = fs.readdirSync('data/images');
    const url = 'http://localhost:8080/images/';
    res.send({
      data: data.map(item => ({
        name: item,
        id: uuid(),
        src: url + item,
      })),
      status: 0,
    });
  }

5.删文件

fs.unlinkSync(文件名)

  @Get('/image/delete')
  deleteImage(@Query() query, @Res() res): void {
    const files = fs.readdirSync('data/images');
    const target = files.filter(item => item === query.name);
    if (target) {
      fs.unlinkSync('data/images/' + target);
      res.send({status: 0 });
    }
    res.send({status: 1 });
  }

案例

用useEffect代替了didMount请求图片列表

const [list, setList] = useState([]);

useEffect(() => { 
    getAndUpdateImageList(setList);
},[]);

import React,{useState, useEffect} from 'react';
import UploadImage from "./component/upload-image/upload-image";
import axios from "axios";
import {message} from "antd";

const baseUrl = 'http://localhost:8080/image';

const getImageListUrl = `${baseUrl}/list`;
const addImageUrl = `${baseUrl}/add`;
const deleteImageUrl = `${baseUrl}/delete`;

const ajax = (url, data={}, type='GET') =>{
    return new Promise((resolve)=>{
        const promise = type === 'GET' ? axios.get(url, {params: data}) : axios.post(url, data)
        promise.then(res=>{
            const data = res.data;
            data.status !== 0 ? message.error(data.msg) : resolve(data);
        }).catch(err => {
            message.error('Network request Error: '+err);
        })
    })
};

const getAndUpdateImageList = async(setList) => {
    const data = await ajax(getImageListUrl);
    setList(data.data);
};

const deleteImage = async ({name}, setList)=>{
    await ajax(deleteImageUrl,{name});
    getAndUpdateImageList(setList);
};

const uploadImage = (item, setList) => {
    getAndUpdateImageList(setList);
};

const downloadImage = (item) => {
    console.log('downloadImage', item)
};

function App() {
    const [list, setList] = useState([]);

    useEffect(() => {
        getAndUpdateImageList(setList);
    },[]);

    return (
      
        uploadImage(item, setList)}
            onDelete={(item)=>deleteImage(item, setList)}
            onDownload={(item)=>downloadImage(item)}
        />
      
  );
}

export default App;

源码

https://github.com/shenleStm/Upload-Image

[React+Nest.js]仿Antd实现一个图片上传的组件