use ESBuild to bundle and transpile typescript files to javascript

esbuild.ts

import * as esbuild from "esbuild-wasm"
import esbuildWasmUrl from "esbuild-wasm/esbuild.wasm?url"
import Path from "path"

let isEsbuildWasmInitialized = false

export const tsToJs = async (tree: Record<string, string>) => {
  if (!isEsbuildWasmInitialized) {
    await esbuild.initialize({ wasmURL: esbuildWasmUrl })
    isEsbuildWasmInitialized = true
  }

  const out = await esbuild.build({
    entryPoints: ["index.ts"],
    plugins: [ESBuildFakeFS(tree)],
    logOverride: { "commonjs-variable-in-esm": "silent" },
    bundle: true,
    write: false,
  })
  return out.outputFiles[0].text
}

// mostly from: https://github.com/evanw/esbuild/issues/1952
const ESBuildFakeFS = (tree: Record<string, string>) => {
  const map = new Map(Object.entries(tree))

  return {
    name: "ESBuildFakeFS",
    setup: (build: esbuild.PluginBuild) => {
      build.onResolve({ filter: /.*/, }, (args: esbuild.OnResolveArgs) => {
        if (args.kind === "entry-point")
          return { path: `/${args.path}` }
        if (args.kind === "import-statement") {
          const dirname = Path.dirname(args.importer)
          const path = Path.join(dirname, args.path)
          return { path }
        }
        throw Error("not resolvable")
      })
      build.onLoad({ filter: /.*/ }, (args: esbuild.OnLoadArgs) => {
        const path = map.has(args.path) ? args.path : `${args.path}.ts`
        if (!map.has(path))
          throw Error("not loadable")
        const ext = Path.extname(path)
        const contents = map.get(path)!
        const loader = ({ ".ts": "ts", ".tsx": "tsx", ".js": "js", ".jsx": "jsx" }[ext]) as esbuild.Loader || "default"
        return { contents, loader }
      })

    }
  }
}

example.ts

const scraperCode = import.meta.glob("../scrapers/*.ts", { as: "raw" })

const fetchAwardAvailability = async ({ signal, meta, queryKey }: ReactQuery.QueryFunctionContext) => {
  const scraperQuery = meta as ScraperForRoute
  const scraperPath = (name: string) => {
    const localPath = Object.keys(scraperCode).find((scraperKey) => scraperKey.indexOf(`${name}.ts`) > -1)
    if (!localPath) throw new Error(`Could not find scraper ${name}`)
    return localPath
  }

  const jsCode = await tsToJs({
    "/index.ts": scraperCode[scraperPath(scraperQuery.scraper)] as unknown as string,
    "/common.ts": scraperCode[scraperPath("common")] as unknown as string
  })

  const postData: { code: string, context: ScraperQuery } = { code: jsCode, context: scraperQuery }
  // axios post...
  return scraperResults.flightsWithFares
}