koa-static-middleware/middleware.js

Lightweight static files middleware for Koa2

const fs = require('fs');
const path = require('path');
const Promise = require('bluebird');
const send = require('koa-send');

const stat = Promise.promisify(fs.stat);

module.exports = (root) => {
  if (typeof root !== 'string') throw new Error('root must be a string');

  return async (ctx, next) => {
    const filepath = path.join(root, ctx.path);

    const fileExists = await new Promise((resolve) => {
      fs.exists(filepath, (exists) => {
        resolve(exists);
      });
    });

    const stats = await stat(filepath);

    if (!fileExists || stats.isDirectory()) {
      await next();
    } else {
      await send(ctx, ctx.path, { root });
    }
  };
};