[javascript] Basic Ajax send/receive with node.js

So I'm trying to make a very basic node.js server that with take in a request for a string, randomly select one from an array and return the selected string. Unfortunately I'm running into a few problems.

Here's the front end:

function newGame()
{
   guessCnt=0;
   guess="";
   server();
   displayHash();
   displayGuessStr();
   displayGuessCnt();
}

function server()
{
   xmlhttp = new XMLHttpRequest();

   xmlhttp.open("GET","server.js", true);
   xmlhttp.send();

   string=xmlhttp.responseText;
}

This should send the request to server.js:

var http = require('http');

var choices=["hello world", "goodbye world"];

console.log("server initialized");

http.createServer(function(request, response)
{
    console.log("request recieved");
    var string = choices[Math.floor(Math.random()*choices.length)];
    console.log("string '" + string + "' chosen");
    response.on(string);
    console.log("string sent");
}).listen(8001);

So clearly there are several things going wrong here:

1. I get the feeling the way I am "connecting" these two files isn't correct both in the xmlhttp.open method and in using response.on to send the string back to the front end.

2. I'm a little confused with how I call this page on localhost. The front end is named index.html and the sever posts to 8001. What address should I be go to on localhost in order to access the initial html page after I have initialized server.js? Should I change it to .listen(index.html) or something like that?

3. are there other obvious problems with how I am implementing this (using .responsetext etc.)

(sorry for the long multi-question post but the various tutorials and the node.js source all assume that the user already has an understanding of these things.)

I was facing following error with code (nodejs 0.10.13), provided by ampersand:

origin is not allowed by access-control-allow-origin

Issue was resolved changing

response.writeHead(200, {"Content-Type": "text/plain"});

to

response.writeHead(200, {
                 'Content-Type': 'text/html',
                 'Access-Control-Allow-Origin' : '*'});

RESTful API (Route):

rtr.route('/testing')
.get((req, res)=>{
    res.render('test')
})
.post((req, res, next)=>{
       res.render('test')
})

AJAX Code:

$(function(){
$('#anyid').on('click', function(e){
    e.preventDefault()
    $.ajax({
        url: '/testing',
        method: 'GET',
        contentType: 'application/json',
        success: function(res){
            console.log('GET Request')
        }
    })
})

$('#anyid').on('submit', function(e){
    e.preventDefault()
    $.ajax({
        url: '/testing',
        method: 'POST',
        contentType: 'application/json',
        data: JSON.stringify({
            info: "put data here to pass in JSON format."
        }),
        success: function(res){
            console.log('POST Request')
        }
    })
})
})

Here is a fully functional example of what you are trying to accomplish. I created the example inside of hyperdev rather than jsFiddle so that you could see the server-side and client-side code.

View Code: https://hyperdev.com/#!/project/destiny-authorization

View Working Application: https://destiny-authorization.hyperdev.space/

This code creates a handler for a get request that returns a random string:

app.get("/string", function(req, res) {
    var strings = ["string1", "string2", "string3"]
    var n = Math.floor(Math.random() * strings.length)
    res.send(strings[n])
});

This jQuery code then makes the ajax request and receives the random string from the server.

$.get("/string", function(string) {
  $('#txtString').val(string);
});

Note that this example is based on code from Jamund Ferguson's answer so if you find this useful be sure to upvote him as well. I just thought this example would help you to see how everything fits together.

Express makes this kind of stuff really intuitive. The syntax looks like below :

var app = require('express').createServer();
app.get("/string", function(req, res) {
    var strings = ["rad", "bla", "ska"]
    var n = Math.floor(Math.random() * strings.length)
    res.send(strings[n])
})
app.listen(8001)

https://expressjs.com

If you're using jQuery on the client side you can do something like this:

$.get("/string", function(string) {
    alert(string)
})