JavaScript 前端下载链接图片并上传至服务器或 OSS 的实现方案

// 判断链接是否指向图片且可下载
export const checkImgExists = (imgurl: string) => {
 return new Promise(function (resolve, reject) {
  var ImgObj = new Image();
  ImgObj.src = imgurl;
  ImgObj.onload = function (res) {
   resolve(res);
  };
  ImgObj.onerror = function (err) {
   reject(err);
  };
 });
};

// how to use it
checkImgExists(imgLink)
 .then(() => {
  // do something with imgLink
  console.log(imgLink);
 })
 .catch((err) => {
  // some log or alarm
  console.log(err);
  console.log("很抱歉, 该链接无法获取图片");
 });

下载图片并转换为 Blob

// 将图片链接中的图片进行 XMLHttpRequest 请求，返回Blob对象
function getImageBlob(url: string) {
 return new Promise(function (resolve, reject) {
  var xhr = new XMLHttpRequest();
  xhr.open("get", url, true);
  xhr.responseType = "blob";
  xhr.onload = function () {
   if (this.status == 200) {
    resolve(this.response);
   }
  };
  xhr.onerror = reject;
  xhr.send();
 });
}

// 将Blob对象转为File对象
const blobToFile = (blob: Blob, fileName: string) => {
 return new window.File([blob], fileName, { type: blob.type });
};

// how to use it
// 返回一个File对象，可使用该 File 对象进行上传操作
getImageBlob(src).then(async (res: any) => {
 const srcSplit = src.split("/");
 const filename = srcSplit[srcSplit.length - 1];
 return blobToFile(res, filename);
});

上传至阿里云 OSS 示例

import OSS from "ali-oss";

const ERROR_TIP = "上传失败！";

/**
 * File上传OSS的示例
 * 相关accessKeyId、bucket等参数需要根据你的OSS库进行填写
 * 建议将【accessKeyId，accessKeySecret】这两个敏感信息做成接口获取或者加密
 */
export const uploadToOSS = async (
 fileName: string,
 file: File,
 accessKeyId: string,
 accessKeySecret: string,
 ...props
) => {
 let client = new OSS({
  endpoint, // 你申请好的oss项目地址
  bucket, // OSS 对象载体
  accessKeyId, // your accessKeyId with OSS
  accessKeySecret, // your accessKeySecret with OSS
  internal: true,
  ...props,
 });
 const putResult = await client.put(fileName, file, {
  timeout: 60 * 1000 * 2,
 });
 if (putResult.res.status === 200) {
  return { url: putResult.url, fileName };
 }
 throw new Error(ERROR_TIP);
};

上传至自建服务器方案

// 将Blob对象转为FormData对象
const blobToFormData = (blob: Blob, fileName: string) => {
 const formdata = new FormData();
 formdata.append("file", blob, fileName);
 return formdata;
};

// XMLHttpRequest
const uploadFile = (formData: FormData) => {
 const url = "your_interface";
 let xhr = new XMLHttpRequest();
 xhr.onload = function () {
  console.log("ok");
  console.log(JSON.parse(xhr.responseText));
 };
 xhr.onerror = function () {
  console.log("fail");
 };
 xhr.open("post", url, true);
 xhr.send(formData);
};

// Ajax
const uploadFile2 = (formData: FormData) => {
 const url = "your_interface";
 $.ajax({
  url,
  type: "POST",
  data: formData,
  async: false,
  cache: false,
  contentType: false,
  processData: false,
  success: function (returndata) {
   console.log(returndata);
  },
  error: function (returndata) {
   console.log(returndata);
  },
 });
};

Node.js 后端接收与处理

const express = require("express");
const listenNumber = 5000;
const app = express();
const bodyParser = require("body-parser");
const http = require("http"); //创建服务器的
const formidable = require("formidable");
const path = require("path");
const fs = require("fs");
app.use(express.static("../../upload"));
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json()); //数据JSON类型

// 上传图片
app.post("/upLoadArticlePicture", (req, res, next) => {
 let defaultPath = "../../upload/";
 let uploadDir = path.join(__dirname, defaultPath);
 let form = new formidable.IncomingForm();
 let getRandomID = () =>
  Number(Math.random().toString().substr(4, 10) + Date.now()).toString(36);
 form.uploadDir = uploadDir; //设置上传文件的缓存目录
 form.encoding = "utf-8"; //设置编辑
 form.keepExtensions = true; //保留后缀
 form.maxFieldsSize = 2 * 1024 * 1024; //文件大小
 form.parse(req, function (err, fields, files) {
  if (err) {
   res.locals.error = err;
   res.render("index", { title: TITLE });
   return;
  }
  let filePath = files.file["path"];
  let backName = filePath.split(".")[1];
  let oldPath = filePath.split("\\")[filePath.split("\\").length - 1];
  let newPath = `${getRandomID()}.${backName}`;
  fs.rename(defaultPath + oldPath, defaultPath + newPath, (err) => {
   if (!err) {
    newPath = `http://localhost:${listenNumber}/${newPath}`;
    res.json({ flag: true, path: newPath });
   } else {
    res.json({ flag: false, path: "" });
   }
  });
 });
});