通过js将base64转化成文件

可以通过以下步骤将 base64 转换为文件：

1. 将 base64 字符串转换为 ArrayBuffer 对象：

function base64ToArrayBuffer(base64) {
  const binaryString = window.atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }
  return bytes.buffer;
}

2. 将 ArrayBuffer 对象转换为 Blob 对象：

function arrayBufferToBlob(buffer, type) {
  return new Blob([buffer], { type: type });
}

3. 将 Blob 对象保存为文件：

function saveFile(blob, fileName) {
  const link = document.createElement('a');
  link.href = URL.createObjectURL(blob);
  link.download = fileName;
  link.click();
}

完整代码如下：

function base64ToArrayBuffer(base64) {
  const binaryString = window.atob(base64);
  const len = binaryString.length;
  const bytes = new Uint8Array(len);
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }
  return bytes.buffer;
}

function arrayBufferToBlob(buffer, type) {
  return new Blob([buffer], { type: type });
}

function saveFile(blob, fileName) {
  const link = document.createElement('a');
  link.href = URL.createObjectURL(blob);
  link.download = fileName;
  link.click();
}

// 示例
const base64String = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADIA...';
const arrayBuffer = base64ToArrayBuffer(base64String.split(',')[1]);
const blob = arrayBufferToBlob(arrayBuffer, 'image/png');
saveFile(blob, 'image.png');