download image from yuque exported markdown file

index.mjs

import { remark } from 'remark';
import path from 'path';
import fs from 'fs/promises';
import { selectAll } from 'unist-util-select';
import { glob } from 'glob';
import { createWriteStream } from 'fs';
import { pipeline } from 'stream/promises';
import { request } from 'undici';
import { pinyin } from 'pinyin-pro';

export async function run() {
  const files = await glob('**/*.md', {
    ignore: 'node_modules/**'
  });
  for (let file of files) {
    const doc = await fs.readFile(file);
    console.log(`start handle ${file}`);
    const content = await remark()
    .data('settings', { bullet: '-', listItemIndent: 'one' })
    .use([
      [ replaceHTML ],
      // [ relativeLink, { doc, mapping }],
      [ downloadAsset, { filePath: file } ],
    ])
    .process(doc.toString());
    await writeFile(file, content.toString());
    console.log(`finish write file ${file}`);
  }
}

function downloadAsset(opts) {
  return async tree => {
    const docFilePath = opts.filePath;
    const base = pinyin(path.basename(docFilePath, '.md'), {
      toneType: 'none',
      type: 'array',
      nonZh: 'consecutive',
    }).map(o => o.trim()).join('_');
    const assetsDir = path.join(docFilePath.split('/')[0], 'assets', base);

    const assetNodes = selectAll('image[url^=http]', tree);
    for (const node of assetNodes) {
      const assetName = new URL(node.url).pathname.split('/').pop();
      const filePath = path.join(assetsDir, assetName);
      await download(node.url, path.join('./', filePath), { headers: { 'User-Agent': 'yuque-exporter' } });
      node.url = path.relative(path.dirname(docFilePath), filePath);
    }
  };
}

function replaceHTML() {
  return tree => {
    const htmlNodes = selectAll('html', tree);
    for (const node of htmlNodes) {
      if (node.value === '<br />' || node.value === '<br/>') {
        node.type = 'text';
        node.value = '\n';
      }
    }
  };
}

async function download(url, filePath, opts = {}) {
  const { headers, ...otherOpts } = opts;
  const { body, statusCode } = await request(url, {
    headers: {
      'User-Agent': 'yuque-exporter',
      ...headers,
    },
    maxRedirections: 10,
    ...otherOpts,
  });

  if (statusCode !== 200) {
    return url;
  }

  await mkdir(path.dirname(filePath));
  await pipeline(body, createWriteStream(filePath));

  return filePath;
}

async function mkdir(p) {
  await fs.mkdir(p, { recursive: true });
}


async function writeFile(filePath, content) {
  await fs.mkdir(path.dirname(filePath), { recursive: true });
  content = typeof content === 'string' || Buffer.isBuffer(content) ? content : JSON.stringify(content, null, 2);
  await fs.writeFile(filePath, content, 'utf-8');
}

run();

use

$ npm i remark unist-util-select glob undici pinyin-pro
$ node index.mjs

The minimum required version of node is 18.

The majority of the code was copied from https://github.com/atian25/yuque-exporter/blob/master/src/lib/doc.ts.