This topic provides sample code that shows how to request a JavaScript file and return the file to the client.

Sample code

 * The sample code shows how to request the file and return the file to the client.
 * Replace someHost and url with your host and URL addresses during the test.
const someHost = ""
const url = someHost + "qrcode.js"
 * Use gatherResponse to obtain the response body and return it to the client as a string.
 * Use await gatherResponse(..) in an asynchronous function to ensure that the whole response body is obtained.
async function gatherResponse(response) {
  const headers = response.headers
  const contentType = headers.get("content-type") || ""
  if (contentType.includes("application/json")) {
    return JSON.stringify(await response.json())
  } else if (contentType.includes("application/text")) {
    return response.text()
  } else if (contentType.includes("text/html;charset=UTF-8")) {
    return response.text()
  } else {
    return response.blob()

async function handleRequest() {
  const init = {
    headers: {
      "content-type": "application/json;charset=UTF-8",
  const response = await fetch(url, init)
  const results = await gatherResponse(response)
  return new Response(results, init)

addEventListener("fetch", event => {
  return event.respondWith(handleRequest())


A request to fetch the file is sent in EdgeRoutine and the file is returned to the client.