element upload上传图片后台收不到图片信息

Question

<el-form-item label="图片" >
    <el-upload
        class="upload-demo"
        ref="upload"
        drag
        :action="form.uploadUrl"
        :data="form.upLoadData"
        :onError="uploadError"
        :onSuccess="uploadSuccess"
        :before-upload="beforeImgUpload"
        multiple>
        <i class="el-icon-upload"></i>
        <div class="el-upload__text">将文件拖到此处，或<em>选择文件</em></div>
        <div class="el-upload__tip" slot="tip">请上传jpg/png文件，且不超过500kb</div>
    </el-upload>
    <img :src="dataUrl" />
</el-form-item>

return {
    form: {
        ac_name: '',
        ac_id:'',
        ac_start_time: '',
        ac_end_time:'',
        uploadUrl:'http://www.youxia.com/yxcard/admin.php?s=/Activity/upload_img',
        upLoadData:{
            img_base64:"",
            type:1
        },
        fileList:[],
        ac_content: ''
    },
    dataUrl:''
}
    

 // 文件上传前
beforeImgUpload (file) {
    const self = this;  //这个很重要！
    var reader = new FileReader();
    reader.readAsDataURL(file);
    reader.onloadend = function() {
        self.form.upLoadData.img_base64 = this.result;
        console.log(self.form.upLoadData.img_base64);
    };
},

// 上传成功后的回调
uploadSuccess (response, file, fileList) {
    console.log('上传文件', response)
    this.$alert(response.retData.msg);
    console.log(this.form.upLoadData.img_base64);
},

我的beforeImgUpload 已经给upLoadData.img_base6赋值了 ，为什么后台接口收不到数据？type=1能收到，回调成功的upLoadData.img_base64也能打出来，但是后台显示的upLoadData.img_base64就是空的。

Answer 1

你回调成功打印的upLoadData.img_base64还是组件内部的数据, 并不是uploadSuccess回调传回来的数据, 最好可以看下 回调的response和你的请求信息

Answer 2

reader.onloadend是异步请求