您现在的位置是：网站首页> 编程资料编程资料

解决vue中reader.onload读取文件的异步问题_vue.js_

2023-05-24 318人已围观

简介解决vue中reader.onload读取文件的异步问题_vue.js_

reader.onload读取文件的异步问题

问题

用element上传文件组件上传文件，然后在前端读取，由于reader.onload读取文件是异步的会造成return回去的数据无法被获取

export function import_excel_to_json(file){ let jsonData = {} let reader = new FileReader() reader.readAsArrayBuffer(file) reader.onload = function () { let buffer = reader.result let bytes = new Uint8Array(buffer) let length = bytes.byteLength let binary = '' for (let i = 0; i < length; i++) { binary += String.fromCharCode(bytes[i]) } let XLSX = require('xlsx') let wb = XLSX.read(binary, { type: 'binary' }) wb.SheetNames.map(item=>{ jsonData[item] = XLSX.utils.sheet_to_json(wb.Sheets[item]) jsonData[item].shift() }) return jsonData } }) }

在外部调用该函数：

let data = this.import_excel_to_json(File)

data获取不到返回值

解决

用Promise进行处理

export function import_excel_to_json(file){ return new Promise(function (resolve, reject) { let jsonData = {} let reader = new FileReader() reader.readAsArrayBuffer(file) reader.onload = function () { let buffer = reader.result let bytes = new Uint8Array(buffer) let length = bytes.byteLength let binary = '' for (let i = 0; i < length; i++) { binary += String.fromCharCode(bytes[i]) } let XLSX = require('xlsx') let wb = XLSX.read(binary, { type: 'binary' }) wb.SheetNames.map(item=>{ jsonData[item] = XLSX.utils.sheet_to_json(wb.Sheets[item]) jsonData[item].shift() }) resolve(jsonData); } }) }