详解Element-UI中上传的文件前端处理

Element-UI对于文件上传组件的功能点着重于文件传递到后台处理，所以要求action为必填属性

Element-UI对于文件上传组件的功能点着重于文件传递到后台处理，所以要求action为必填属性。但是如果需要读取本地文件并在前端直接处理，文件就没有必要传递到后台，比如在本地打开一个JSON文件，利用JSON文件在前端进行动态展示等等。 下面就展示一下具体做法：

首先定义一个jsonContent, 我们的目标是将本地选取的文件转换为JSON赋值给jsonContent

然后我们的模板文件是利用el-dialog和el-upload两个组件组合：这里停止文件自动上传模式:auto-upload="false"

 <el-button type="primary" @click="dialogVisible = true">Load from File</el-button>
 <el-dialog title="Load JSON document from file" :visible.sync="dialogVisible">
 <el-upload :file-list="uploadFiles" action="alert" :auto-upload="false" multiple :on-change="loadJsonFromFile">
 <el-button size="small" type="primary">Select a file</el-button>
 <div slot="tip">upload only jpg/png files, and less than 500kb</div>
 </el-upload>
 <span slot="footer">
 <el-button type="primary" @click="dialogVisible = false">cancel</el-button>
 <el-button type="primary" @click="loadJsonFromFileConfirmed">confirm</el-button>
 </span>
 </el-dialog>

最后通过html5的filereader对变量uploadFiles中的文件进行读取并赋值给jsonContent

if (this.uploadFiles) {
 for (let i = 0; i < this.uploadFiles.length; i++) {
 let file = this.uploadFiles[i]
 console.log(file.raw)
 if (!file) continue
 let reader = new FileReader()
 reader.onload = async (e) => {
 try {
 let document = JSON.parse(e.target.result)
 console.log(document)
 } catch (err) {
 console.log(`load JSON document from file error: ${err.message}`)
 this.showSnackbar(`Load JSON document from file error: ${err.message}`, 4000)
 }
 }
 reader.readAsText(file.raw)
 }
 }

为方便测试，以下是完整代码：

另外一篇文章是介绍如何将jsonContent变量中的JSON对象保存到本地文件

<template>
 <div>
 <el-button type="primary" @click="dialogVisible = true">Load from File</el-button>
 <el-dialog title="Load JSON document from file" :visible.sync="dialogVisible">
 <el-upload :file-list="uploadFiles" action="alert" :auto-upload="false" multiple :on-change="loadJsonFromFile">
 <el-button size="small" type="primary">Select a file</el-button>
 <div slot="tip">upload only jpg/png files, and less than 500kb</div>
 </el-upload>
 <span slot="footer">
 <el-button type="primary" @click="dialogVisible = false">cancel</el-button>
 <el-button type="primary" @click="loadJsonFromFileConfirmed">confirm</el-button>
 </span>
 </el-dialog>
</div>
 
</template>
 
<script>
export default {
 data () {
 return {
 // data for upload files
 uploadFilename: null,
 uploadFiles: [],
 dialogVisible: false
 }
 },
 methods: {
 loadJsonFromFile (file, fileList) {
 this.uploadFilename = file.name
 this.uploadFiles = fileList
 },
 loadJsonFromFileConfirmed () {
 console.log(this.uploadFiles)
 if (this.uploadFiles) {
 for (let i = 0; i < this.uploadFiles.length; i++) {
 let file = this.uploadFiles[i]
 console.log(file.raw)
 if (!file) continue
 let reader = new FileReader()
 reader.onload = async (e) => {
 try {
 let document = JSON.parse(e.target.result)
 console.log(document)
 } catch (err) {
 console.log(`load JSON document from file error: ${err.message}`)
 this.showSnackbar(`Load JSON document from file error: ${err.message}`, 4000)
 }
 }
 reader.readAsText(file.raw)
 }
 }
 this.dialogVisible = false
 }
 }
}
</script>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。