使用javascript将base64string转换为可下载文件

function downloadFileFromBase64(base64String, fileName) {
  // 将Base64字符串转换为字节数组
  var byteCharacters = atob(base64String);

  // 创建字节数组的缓冲区
  var byteArrays = [];

  for (var offset = 0; offset < byteCharacters.length; offset += 512) {
    var slice = byteCharacters.slice(offset, offset + 512);

    var byteNumbers = new Array(slice.length);
    for (var i = 0; i < slice.length; i++) {
      byteNumbers[i] = slice.charCodeAt(i);
    }

    var byteArray = new Uint8Array(byteNumbers);
    byteArrays.push(byteArray);
  }

  // 创建Blob对象
  var blob = new Blob(byteArrays, { type: 'application/octet-stream' });

  // 创建URL对象
  var url = URL.createObjectURL(blob);

  // 创建<a>标签并设置属性
  var link = document.createElement('a');
  link.href = url;
  link.download = fileName;

  // 模拟点击事件，触发文件下载
  link.click();

  // 释放URL对象
  URL.revokeObjectURL(url);
}

var base64String = 'SGVsbG8gd29ybGQh';
var fileName = 'hello.txt';

downloadFileFromBase64(base64String, fileName);