文件file对象转换为base64格式数据

function getBase64 (file) {
    return new Promise(function (resolve, reject) {
      let reader = new FileReader()
      let imgResult = ‘‘
      reader.readAsDataURL(file)
      reader.onload = function () {
        imgResult = reader.result
      }
      reader.onerror = function (error) {
        reject(error)
      }
      reader.onloadend = function () {
        resolve(imgResult)
      }
    })
};
export default getBase64;