Js上传图片文件获取Base64位格式预览

 <input type="file" accept="image/*"  @change="changeFile" />

const changeFile= (e) => {
    let reader = new FileReader()
    reader.readAsDataURL(e.target.files[0])
    reader.onload = (res) => {
       res.target.result // 赋值到图片src
    }
}