摘要：最近在做一個項目，需要在前端對圖片切片并上傳到七牛云技術要點可將保存成二進制文件將二進制文件添加到中上傳數據到后端處理代碼實現目前沒有看到七牛云提供的支持上傳到云上的，所以這里自己實現了一下注意到七牛云的時候不要設置，讓瀏覽器自己處理請求

最近在做一個項目，需要在前端對圖片切片并上傳到七牛云

canvas.toBlob(blob=>{}); //可將canvas保存成二進制文件

formData.append("file", blob, "filename"); //將二進制文件添加到FormData中

ajax.send(formData); //上傳數據到后端處理

目前沒有看到七牛云提供的JSSDK支持上傳blob到云上的， 所以這里自己實現了一下
注意ajax post formData到七牛云的時候不要設置content-type，讓瀏覽器自己處理

class Qiniu {
  constructor(options = {}) {
    this._options = {...options};
  }

  ajax(url = "", opt = {}) {
    const options = {method: "GET", async: true, dataType: "JSON", ...opt};
    return new Promise((resolve, reject) => {
      const ajax = this.createAjax();
      if (ajax) {
        const _async = typeof options.async === "boolean" ? options.async : true;
        ajax.open(options.method || "GET", url, _async);
        if (options.headers) {
          Object.keys(options.headers).forEach(key => {
            ajax.setRequestHeader(key, options.headers[key]);
          });
        }
        ajax.onreadystatechange = () => {
          if (ajax.readyState === 4) {
            if (ajax.status >= 200 && ajax.status <= 400) {
              let res = ajax.responseText;
              if (options.dataType && options.dataType.toUpperCase() === "JSON") {
                res = JSON.parse(res);
              }
              resolve(res, ajax.response);
            } else {
              reject(new Error("請求失敗:" + ajax.status))
            }
          }
        };
        ajax.send(options.data);
      } else {
        reject(new Error("創建Ajax請求失敗！"));
      }
    });
  }

  createAjax() {
    let xmlhttp;
    if (window.XMLHttpRequest) {
      xmlhttp = new XMLHttpRequest();
    } else {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    return xmlhttp;
  }

  getToken() {
    if (this._options.token) {
      return Promise.resolve(this._options.token);
    } else {
      if (typeof this._options.getToken === "function") {
        const t = this._options.getToken();
        if (t && typeof  t.then === "function") {
          return t.then(token => {
            this._options.token = token;
            return token;
          })
        } else if (typeof t === "string") {
          this._options.token = t;
          return Promise.resolve(t);
        } else {
          return Promise.reject(new Error("options.getToken必須返回Promise或string token"));
        }
      } else if (typeof this._options.getTokenUrl === "string") {
        return this.ajax(this._options.getTokenUrl, {
          headers: {
            authorization: this._options.authorization
          }
        }).then(res => {
          this._options.token = res.uptoken;
          return this._options.token;
        }).catch(ex => {
          throw new Error("獲取uptoken失敗:" + ex.message);
        });
      } else {
        return Promise.reject(new Error("無法獲取token"));
      }
    }
  }

  upload(file, filename, key) {
    return this.getToken().then(token => {
      const formData = new FormData();
      formData.append("key", key || filename);
      formData.append("token", token);
      formData.append("file", file, filename);
      return formData;
    }).then(data => {
            //注意不要設置content-type,瀏覽器自動會填充
      return this.ajax("http://upload.qiniu.com/", {
        method: "POST",
        data,
      });
    });
  }
}


canvas.toBlob(blob => {
    const filename = Date.now() + Math.random() + ".png";
    const qiniu = new Qiniu({getTokenUrl:"這里寫獲取七牛token的接口地址"});
    qiniu.upload(blob, filename);
}, "image/png");