Rest API Service problem from javascript

Hi,

I'm trying to create a function call to a service with javascript.

This is my code:

var data = "{\n\t\"input\":{\n\t\t\"space\": \"Hki Pa A 109\",\n\t\t\"type\": \"TEMP\"\n\t}\t\n}";

var xhr = new XMLHttpRequest();

xhr.withCredentials = true;

xhr.addEventListener("readystatechange", function () {

  if (this.readyState === 4) {

console.log(this.responseText);

  }

});

xhr.open("POST", "https://server-address/Thingworx/Things/PWIMAPI/Services/GetMeasurementPoints");

xhr.setRequestHeader("accept", "application/json");

xhr.setRequestHeader("content-type", "application/json");

xhr.setRequestHeader("appkey", "my-app-key");

xhr.setRequestHeader("cache-control", "no-cache");

xhr.send(data);

If I run this in postman it returns the correct json-content, but when I run it in a HTML-file on the server I get:

Status Code:

401 Unauthorized

Have anyone had a similar problem before? Any suggestion how to solve this?