JavaScript不同场景下的文件下载方案详解

  <a 
     href="https://images.unsplash.com/photo-1682687982468-4584ff11f88a?ixlib=rb-4.0.3&q=85&fm=jpg&crop=entropy&cs=srgb&dl=neom-xDQKvPjxtxo-unsplash.jpg" 
     download="demo">下载图片</a>

function downLoadFile(res){
    const ele = document.createElement('a');
          ele.setAttribute('href',res.url); //设置下载文件的url地址
          ele.setAttribute('download' , 'download');//用于设置下载文件的文件名
          ele.click();
  
    link.addEventListener('click', (event) => {
      event.preventDefault();
      const downloadTimer = setTimeout(() => {
        alert('下载超时，请重试！');
      }, 5000); 

      const errorListener = () => {
        clearTimeout(downloadTimer);
        alert('下载失败！');
        link.removeEventListener('error', errorListener);
      };

      link.addEventListener('error', errorListener);
  });
}

window.onload = function(){
    $.ajax({
        url:"api/file/download",
        type:"get",
        dataType:'JSON'
    }).then(function(res){
        if(res.bizNO > 0 ){
            downLoadFile(res);
        }else{
            alert(res.bizMsg);
        }
   }).always(function(){
        alert("连接异常")；
    })
}

function fileDownLoad(data){
    // 1. 创建点击下载的元素   
    var linkElement = document.createElement('a');
  
    // 2. 判断浏览器是否支持blob对象
    try{
        //该实例化的方式第一个参数必须是数组的格式
        var blob = new Blob([data],{
          type: "application/pdf"
        });
    }catch(e){
        //旧版本浏览器下的blob创建对象
        window.BlobBuilder = window.BlobBuilder ||
                             window.WebKitBlobBuilder ||
                             window.MozBlobBuilder ||
                             window.MSBlobBuilder;
        if(e.name == 'TypeError' && window.BlobBuilder){
            var blobbuilder = new BlobBuilder();
            BlobBuilder.append(data);
            var blob = blobbuilder.getBlob("application/pdf");
        }else{
            alert("浏览器版本较低，暂不支持该文件类型下载");
        }
    }
  
    // 提取blob文件中的url信息，使二进制文件在不读取到js中时直接下载
    let url = window.URL.createObjectURL(blob);
    linkElement.setAttribute('href',url);
    linkElement.setAttribute('downLoad','download');
    linkElement.click();
    
    // 释放URL内存
    window.URL.revokeObjectURL(url);
}

document.querySelector('#fileInput').addEventListener('change', (event)=>{
  fileDownLoad(event.target.files[0])
})

function downloadFileWithToken(url, token) {
    let xhr = new XMLHttpRequest();
    xhr.open('GET', url, true);
    xhr.setRequestHeader("Authorization", token);
    xhr.responseType = 'blob';
    xhr.onload = function (e) {
        if (this.status === 200) {
            let blob = this.response;
            let fileName = '下载的文件名称';
            // 针对IE浏览器          
            if (window.navigator.msSaveBlob) {
                try {
                    window.navigator.msSaveBlob(blob, fileName);
                } catch (e) {
                    console.log(e);
                }
            } else {
                // 通用浏览器   
                const url = window.URL.createObjectURL(blob);
                a.href = url;
                a.download = fileName;
                document.body.appendChild(a);
                a.click();
                document.body.removeChild(a);
                window.URL.revokeObjectURL(url);
            }
        } else {
            alert('下载文件失败');
        }
    }
    xhr.send();
}

import FileSaver from 'file-saver'

let blob = new Blob(["Hello, FileSaver! Blob 下载"], {type: "text/plain;charset=utf-8"});
window.saveAs(blob, "hello FileSaver.txt");

import FileSaver from 'file-saver'

let blob = new Blob(["Hello, FileSaver! URL 下载"], {type: "text/plain;charset=utf-8"});
const url = window.URL.createObjectURL(blob)
window.saveAs(url, "hello FileSaver.txt");