vue element upload实现图片本地预览

<el-upload
 class="avatar-uploader"
 action="123" //这个路径不重要，可以随便写
 :show-file-list="false"
 :on-success="handleAvatarSuccess"
 :on-change="onchange"
 :before-upload="beforeAvatarUpload">
 <img v-if="imageUrl" :src="imageUrl" class="avatar">
 <i v-else class="el-icon-plus avatar-uploader-icon"></i>
</el-upload>

<script>
 export default {
 data() {
 return {
 imageUrl: '',
 };
 },
 methods: {
 handleAvatarSuccess(res, file) {
 this.imageUrl = URL.createObjectURL(file.raw);
 },
 beforeAvatarUpload(file) {
 const isJPG = file.type === 'image/jpeg';
 const isLt2M = file.size / 1024 / 1024 < 2;

 if (!isJPG) {
 this.$message.error('上传头像图片只能是 JPG 格式!');
 }
 if (!isLt2M) {
 this.$message.error('上传头像图片大小不能超过 2MB!');
 }
 return isJPG && isLt2M;
 },
 //当上传图片后，调用onchange方法，获取图片本地路径
 onchange(file,fileList){
 var _this = this;
 var event = event || window.event;
 var file = event.target.files[0];
 var reader = new FileReader(); 
 //转base64
 reader.onload = function(e) {
 _this.imageUrl = e.target.result //将图片路径赋值给src
 }
 reader.readAsDataURL(file);
 }
 }
 }
</script>