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。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。