1. const getFileObj = async (file)=>{
    2.   const reader = new FileReader(); // 创建文件对象
    3.   const imgObj = await new Promise((resolve, reject) => {
    4.     reader.onload = function (evt) {
    5.       const image = new Image();
    6.       image.src = evt.target.result;
    7.       image.onload = function () {
    8.         // 返回图片的宽高
    9.         resolve({
    10.             width: this.width,
    11.           height: this.height
    12.         })
    13.       }
    14.     }
    15.     reader.readAsDataURL(file)
    16.   })
    17.   return imgObj;
    18. }
    20. //上传文件
    21. getFileObj(file).then(res=>{
    22.     console.log(res); // 返回 {width, height}
    23. });