本文将会用typescript+react+react-dropzone+express.js实现前后端上传图片。当然是用typescript需要提前下载相应的模块，在这里就不依依介绍了。

第一步，配置tsconfig.js

    "compilerOptions": { 
            "outDir": "./public/", 
            "sourceMap": true, 
            "noImplicitAny": true, 
            "module": "commonjs", 
            "target": "es5", 
            "jsx": "react" ,
            "noImplicitAny": false,
            "suppressImplicitAnyIndexErrors": true
    },
    "files": [ "./views/home/main.tsx" ],
    "exclude": [
        "node_modules"
    ]
}

2.配置webpack

var path = require('path');
var webpack = require('webpack');
var ExtractTextPlugin = require("extract-text-webpack-plugin");
var HtmlWebpackPlugin = require('html-webpack-plugin');
var title = {
    home: '首页',
}
module.exports = {
    entry: {
        home: [
            'babel-polyfill',
            './views/home/main.tsx'
        ],
        common: ['react','babel-polyfill']
    },
    output: {
        path: path.join(__dirname, 'views/wap'),
        filename: '[name].js',
        chunkFilename: '[id].build.js?[chunkhash]',
        publicPath: '/views/wap/',
    },
    module: {
        loaders: [
            { 
                test: /\.tsx?$/, 
                loader: 'ts-loader' 
            },
            {
                test: /\.(less|css)$/,
                loader: ExtractTextPlugin.extract('style', 'css!less'),
            },
            {         
              test:/\.(js|jsx)?$/,
              loader:'babel',
              exclude:/node_modules/,
              query:{compact:false,presets:['es2015','react','stage-0','stage-1','stage-2']}
            },
            {
                test: /\.(png|jpg|gif)?$/,
                loaders: ['url?limit=8192&name=[name]_[sha512:hash:base64:7].[ext]'],
            },
            {
                test: /\.(eot|woff|ttf|svg)$/,
                loader: 'file?limit=81920&name=[name]_[sha512:hash:base64:7].[ext]'
            },
        ]
    },
    resolve: {
        root: ['node_modules'],
        extensions: ['', '.js', '.jsx', '.html', '.json','.ts', '.tsx'],
        modulesDirectories: ['node_modules'],
        alias: {}
    },
    externals: {},
    plugins: [
        new webpack.DefinePlugin({
            'process.env.NODE_ENV': '"production"'
        }),
        new webpack.HotModuleReplacementPlugin(),
        new ExtractTextPlugin('[name].[contenthash:20].css'),
        new webpack.optimize.UglifyJsPlugin({
            compress: {warnings: false}
        }),
        new webpack.optimize.CommonsChunkPlugin('common', 'common.js'),
            new HtmlWebpackPlugin(
            {
                  title: "",
                  template: path.join(path.resolve(__dirname),'views/wap/myApp.html'),  //模板文件
                  inject:'body',
                  hash:true,    //为静态资源生成hash值
                  minify:{    //压缩HTML文件
                    removeComments:false,    //移除HTML中的注释
                    collapseWhitespace:false    //删除空白符与换行符
                  }
            }
            )
    ]
};

3.react-dropzone

import * as Dropzone from 'react-dropzone';

<Dropzone   accept="image/jpeg, image/png"
            onDrop={(accepted, rejected) => { this.setState({ accepted, rejected });this.drop(accepted[0].preview) }}
            style={{width:"100%",height:"120px",background:"#f2f2f2","padding-top":'90px',"cursor":"pointer","box-sizing":"content-box"}} >
</Dropzone>

accept:表示图片的接受类型
onDrop代表图片加载以后触发
accepted:表示加载图片成功后相关信息，打印出来如下:

Paste_Image.png

rejected：表示加载图片失败后，相关信息：

Paste_Image.png

4.图片处理、上传

新建一个drop方法在触发onDrop后。

drop(src : any) : any{
        const that = this;
        let img = src;
        let image = new Image();
        image.crossOrigin = 'Anonymous';
        image.src = img;
        image.onload = function(){
            let base64 = that.getBase64Image(image);
            that.upLoadImg({imgData:base64})
        }
}

在这里我们使用base64传递，所以我们需要把图片转成base64，定义getBase64Image处理

getBase64Image(img :any) : string {
        let canvas = document.createElement("canvas");
        canvas.width = img.width;
        canvas.height = img.height;
        let ctx = canvas.getContext("2d");
        ctx.drawImage(img, 0, 0, img.width, img.height);
        let ext = img.src.substring(img.src.lastIndexOf(".")+1).toLowerCase();
        let dataURL = canvas.toDataURL("image/"+ext);
        return dataURL;
}

最终返回的是处理后图片的地址，然后上传

async upLoadImg(params : object) : Promise<any>{
        let res  = await axios.post('http://localhost:3000/upLoadImg',params);
}

5.node部分

router/index.js

var express = require('express');
var router = express.Router();
var rf = require('fs');
var SetImg = require('./controller/uploadImg');
var setImg = new SetImg;
router.post('/upLoadImg',setImg.setUploadImg);
module.exports = router;

./controller/uploadImg.js

var rf = require('fs');
class SetImg {
    setUploadImg(req, res, next) {
        let imgData = req.body.imgData;
        let base64Data = imgData.replace(/^data:image\/\w+;base64,/, "");
        let dataBuffer = new Buffer(base64Data, 'base64');
        let timer = Number( new Date() );
        rf.writeFile("views/images/artCover"+timer+".png",dataBuffer, function(err) {
            if(err) {
              res.json({"code":400,"verson":false,"msg":err});
            }else {
              res.json({"code":100,"verson":true,"url":"views/src/common/images/artCover/"+timer+".png"});
            }
        });
    }
}
module.exports = SetImg;

拿到图片后先进行格式转换，然后将图片写入到本地，返回图片路径。

import * as React from 'react';
import * as ReactDom   from 'react-dom';

import * as Dropzone from 'react-dropzone';
import * as axios from 'axios';

import './main.less';

declare var document;
declare var Image;
class ImgUpload extends React.Component<any,any> {
    constructor(){
        super()
        this.state = {
          accepted: [],
          rejected: []
        }
    }
    public drop(src : any) : any{
        const that = this;
        let img = src;
        let image = new Image();
        image.crossOrigin = 'Anonymous';
        image.src = img;
        image.onload = function(){
            let base64 = that.getBase64Image(image);
            console.log(base64)
            that.upLoadImg({imgData:base64})
        }
    }
    //转base64
    public getBase64Image(img :any) : string {
        let canvas = document.createElement("canvas");
        canvas.width = img.width;
        canvas.height = img.height;
        let ctx = canvas.getContext("2d");
        ctx.drawImage(img, 0, 0, img.width, img.height);
        let ext = img.src.substring(img.src.lastIndexOf(".")+1).toLowerCase();
        let dataURL = canvas.toDataURL("image/"+ext);
        return dataURL;
    }
    public async upLoadImg(params : object) : Promise<any>{
        let res  = await axios.post('http://localhost:3000/upLoadImg',params);

    }
    render(){
        const that = this;
        let imgs;
        if(this.state.accepted.length > 0){
            imgs = (
                <ul>
                    {this.state.accepted.map( (f) => {
                        return <img key={f.name} src={f.preview} />
                    })}
                </ul>
            )
        }
        return (
            <div>
                <div className="wrap">
                    <Dropzone
                    accept="image/jpeg, image/png"
                    onDrop={(accepted, rejected) => { console.log(accepted);console.log(rejected);this.setState({ accepted, rejected });this.drop(accepted[0].preview) }}
                    style={{width:"100%",height:"120px",background:"#f2f2f2","padding-top":'90px',"cursor":"pointer","box-sizing":"content-box"}}
                     >
                        <p className="upload">请添加主题图片</p>
                    </Dropzone>
                </div>
                <div className="show">{imgs}    
                </div>  
            </div>
            
        )
    }

}
ReactDom.render(
    <ImgUpload />,
    document.getElementById('app')
)