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js实现点击下载功能

2026-01-31 01:13:32JavaScript

使用 `<a>` 标签实现下载

通过动态创建 <a> 标签并设置 download 属性实现文件下载。适用于已知文件 URL 或 Blob 数据：

function downloadFile(url, filename) {
  const a = document.createElement('a');
  a.href = url;
  a.download = filename || 'downloaded-file';
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
}

使用 Blob 对象下载动态内容

将字符串或二进制数据转换为 Blob 对象生成下载链接，适合动态生成内容的场景：

function downloadTextAsFile(text, filename) {
  const blob = new Blob([text], { type: 'text/plain' });
  const url = URL.createObjectURL(blob);
  downloadFile(url, filename);
  setTimeout(() => URL.revokeObjectURL(url), 100);
}

处理跨域资源下载

当下载跨域资源时，需要先通过 fetch API 获取数据再转换为 Blob：

async function downloadCrossOriginFile(url, filename) {
  const response = await fetch(url);
  const blob = await response.blob();
  const objectUrl = URL.createObjectURL(blob);
  downloadFile(objectUrl, filename);
  setTimeout(() => URL.revokeObjectURL(objectUrl), 100);
}

大文件分块下载

处理大文件下载时可使用流式处理避免内存问题：

async function downloadLargeFile(url, filename) {
  const response = await fetch(url);
  const reader = response.body.getReader();
  const chunks = [];

  while(true) {
    const { done, value } = await reader.read();
    if(done) break;
    chunks.push(value);
  }

  const blob = new Blob(chunks);
  const objectUrl = URL.createObjectURL(blob);
  downloadFile(objectUrl, filename);
  URL.revokeObjectURL(objectUrl);
}

添加下载进度显示

通过监听 fetch 响应进度实现下载进度条：

async function downloadWithProgress(url, filename) {
  const response = await fetch(url);
  const contentLength = +response.headers.get('Content-Length');
  const reader = response.body.getReader();
  let receivedLength = 0;
  const chunks = [];

  while(true) {
    const { done, value } = await reader.read();
    if(done) break;
    chunks.push(value);
    receivedLength += value.length;
    console.log(`Downloaded ${(receivedLength/contentLength*100).toFixed(1)}%`);
  }

  const blob = new Blob(chunks);
  downloadFile(URL.createObjectURL(blob), filename);
}