通过Rest API使用Javascript发送Http POST请求

我正在尝试通过Rest API密钥将Http发布请求发送到parse.com服务器。不知道我是否按照下面的方法正确进行操作。以下是我的整个脚本，并创建一个按钮，该按钮应在简单的HTML页面中触发发布请求。

<input id="clickMe" type="button" value="clickme" onclick="doFunction();" />
<script>

xmlhttp = new XMLHttpRequest();
var url = "https://api.parse.com/1/classes/english";
xmlhttp.open("POST", url, true);
xmlhttp.setRequestHeader("Content-type", "application/json");
xmlhttp.setRequestHeader("X-Parse-Application-Id", "VnxVYV8ndyp6hE7FlPxBdXdhxTCmxX1111111");
xmlhttp.setRequestHeader("X-Parse-REST-API-Key","6QzJ0FRSPIhXbEziFFPs7JvH1l11111111");
xmlhttp.onreadystatechange = function () { //Call a function when the state changes.
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
        alert(xmlhttp.responseText);
    }
}
var parameters = {
    "ephrase": "english",
    "pphrase": "farsi",
     "nvote": 0,
    "yvote": 0
};
// Neither was accepted when I set with parameters="username=myname"+"&password=mypass" as the server may not accept that

function doFunction() {
  xmlhttp.send(parameters);
}

</script>