DOM

<input type="file" name="image" accept="image/*">
<input type="submit" value="上传图片">

Javascript

• 运用 FileReader 将当地图片剖析为base64花样

• 运用 FormData 作为载体将base64图片数据传到背景

var fileInput = document.getElementsByTagName('input')[0],
    submitButton = document.getElementsByTagName('input')[1];
var fileReader = new FileReader(),
    imgData;
    
    //猎取当地图片
    fileInput.addEventListaner('change', function(){
        var file = fileInput.files[0];
        fileReader.readAsDataURL(file);
    }
    
    //将base64花样的图片数据存到imgData
    fileReader.addEventListener('onload', function(){
        imgData = fileReader.result;
    }
    
    //Ajax上传图片数据到背景
    function uploadImg(){
    
        //FormData保留图片信息
        var formData =  new FormData(),
            xhr = new XMLHttpRequest();
        
        formData.append('imgData', imgData);
        
        xhr.open('POST', '/uploadImage', true);
        xhr.send(formData);
    }
    
    submitButton.addEventListener('click', function(){
        uploadImg();
    }
    

Express

• 运用Multipaty剖析表单

var express = require('express');
var router = express.Router();
//引入Multiparty剖析表单
var multiparty = require('multiparty');
var fs = require('fs');

router.post('/uploadImage', function(req, res){
    var form = new multiparty.Form();
    form.parse(req, function(err, fields, files){
        //将前台传来的base64数据去掉前缀
        var imgData = fields.imgData[0].replace(/^data:image\/\w+;base64,/, '');

        var dataBuffer = new Buffer(imgData, 'base64');
        //写入文件
        fs.writeFile('public/images/imge.png', dataBuffer, function(err){
            if(err){
                res.send(err);
            }else{
                res.send('保留胜利');
            }
        });

    });

});