How can I send a value to a ESP8266 through a webpage using AJAX?

Question

I'm working with a NodeMCU ESP8266 and I want to control my WS2812B with it.

So I made a HTML page with an input range and I want to send the value of the range to my ESP8266 - where the website is hosted- by using AJAX .

I only found tutorials on how to send data from an ESP8266 to a webpage and can't find any tutorials on how to send any info to my ESP8266 from a webpage.

The input looks like this:

<input type=range id="rangeinput">

Answer 1

To send a GET request from your webpage with the value you want to send, you can do something like this (untested, so check; I just typed it in, but you get the idea):

var valueToSend = document.getElementById("rangeinput").value;

var ESP8266URL = ""; // URL of ESP8266 page that handles request goes here

var sendValueRequest = new XMLHttpRequest();
sendValueRequest.open("GET", ESP8266URL + "?value=" + valueToSend, true);
sendValueRequest.onreadystatechange = processReturn;
sendValueRequest.send(null);

function processReturn() {
  if (sendValueRequest.readyState == 4 && sendValueRequest.status == 200) {
    var return = sendValueRequest.responseText;
    // Do something (or nothing) with what the server sent back
  }
}

You will have to handle the GET request on the ESP8266. How to do that depends on how the webserver on your ESP8266 is set up.