Element-UI中Upload上传文件前端缓存处理

我就是我 2022-04-23 12:36 155阅读 0赞

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：

<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>

PS： 相关阅读

## [https://developer.mozilla.org...][https_developer.mozilla.org...] ##

作者：java\_augur  
来源：CSDN  
原文：[https://blog.csdn.net/java\_au...][https_blog.csdn.net_java_au...]  
版权声明：本文为博主原创文章，转载请附上博文链接！

来源：[https://segmentfault.com/a/1190000018224949][https_segmentfault.com_a_1190000018224949]

[https_developer.mozilla.org...]: https://developer.mozilla.org/zh-CN/docs/Web/API/FileReader
[https_blog.csdn.net_java_au...]: https://blog.csdn.net/java_augur/article/details/79763505
[https_segmentfault.com_a_1190000018224949]: https://segmentfault.com/a/1190000018224949