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詳解Element-UI中上傳的文件前端處理

更新時(shí)間：2019年08月07日 14:37:16 作者：java_augur

這篇文章主要介紹了詳解Element-UI中上傳的文件前端處理，文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

Element-UI對(duì)于文件上傳組件的功能點(diǎn)著重于文件傳遞到后臺(tái)處理，所以要求action為必填屬性。但是如果需要讀取本地文件并在前端直接處理，文件就沒(méi)有必要傳遞到后臺(tái)，比如在本地打開(kāi)一個(gè)JSON文件，利用JSON文件在前端進(jìn)行動(dòng)態(tài)展示等等。
下面就展示一下具體做法：

首先定義一個(gè)jsonContent, 我們的目標(biāo)是將本地選取的文件轉(zhuǎn)換為JSON賦值給jsonContent

然后我們的模板文件是利用el-dialog和el-upload兩個(gè)組件組合：這里停止文件自動(dòng)上傳模式: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>

最后通過(guò)html5的filereader對(duì)變量uploadFiles中的文件進(jìn)行讀取并賦值給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)
    }
   }

為方便測(cè)試，以下是完整代碼：

另外一篇文章是介紹如何將jsonContent變量中的JSON對(duì)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?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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