1function httpGet(theUrl)
2{
3    var xmlHttp = new XMLHttpRequest();
4    xmlHttp.open( "GET", theUrl, false ); // false for synchronous request
5    xmlHttp.send( null );
6    return xmlHttp.responseText;
7}

1window.onload = function(){
2    var request = new XMLHttpRequest();
3    var params = "UID=CORS&name=CORS";
4
5    request.onreadystatechange = function() {
6        if (this.readyState == 4 && this.status == 200) {
7            console.log(this.responseText);
8        }
9    };
10
11    request.open('POST', 'https://www.example.com/api/createUser', true);
12    request.setRequestHeader('api-key', 'your-api-key');
13    request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
14    request.send(params);
15}
16