Element-UI中Upload上傳文件前端緩存處理

Element-UI對於文件上傳組件的功能點着重於文件傳遞到后台處理，所以要求action為必填屬性。
但是如果需要讀取本地文件並在前端直接處理，文件就沒有必要傳遞到后台，比如在本地打開一個JSON文件，利用JSON文件在前端進行動態展示等等。
下面就展示一下具體做法：
首先定義一個jsonContent, 我們的目標是將本地選取的文件轉換為JSON賦值給jsonContent
然后我們的模板文件是利用el-dialog和el-upload兩個組件組合：這里停止文件自動上傳模式: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html5的filereader對變量uploadFiles中的文件進行讀取並賦值給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)
        }
      }

為方便測試，以下是完整代碼：

<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： 相關閱讀

https://developer.mozilla.org...

作者：java_augur
來源：CSDN
原文：https://blog.csdn.net/java_au...
版權聲明：本文為博主原創文章，轉載請附上博文鏈接！

來源：https://segmentfault.com/a/1190000018224949