a memo of xhr

superwait.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import time
from http.server import (
    BaseHTTPRequestHandler,
    HTTPServer,
)

WAIT_TIME = 1 # sec


class RequestHandler(BaseHTTPRequestHandler):
    def _set_headers(self):
        self.send_response(200)
        self.send_header('Access-Control-Allow-Origin', '*')
        self.end_headers()

    def do_GET(self):
        self._set_headers()
        time.sleep(WAIT_TIME)
        self.wfile.write(b"Hello, world!")


if __name__ == "__main__":
    server_address = ('', 8000)
    httpd = HTTPServer(server_address, RequestHandler)
    httpd.serve_forever()

xhr.html

<script>
function testxhr() {
  return new Promise( (resolve, reject) => {
    const xhr = new XMLHttpRequest();

    xhr.timeout = 500
    xhr.open("GET", "http://localhost:8000/", true)

    xhr.onerror = () => {
      reject(new Error("got onerror"))
    }

    xhr.onabort = () => {
      reject(new Error("got onabort"))
    }

    xhr.ontimeout = () => {
      reject(new Error("got ontimeout"))
    }

    xhr.onreadystatechange = () => {
      if (xhr.readyState !== 4) {
        console.warn(`xhrstate changed ${xhr.readyState}`)
        return
      }

      if (xhr.status === 0) {
        reject(new Error(`xhr.status==${xhr.status} & xhr.readyState==${xhr.readyState}`));
        return
      }

      resolve(xhr.responseText)
    }

    xhr.send(null)
  });
}

(async function() {
  console.log(await testxhr())
})()
</script>