test.js

function getAccessToken(callback) {
	
  $.ajax({
    type: "POST",
    headers: {
      "Authorization": "Basic " + btoa(m_clientID + ":" + m_clientSecret)
    },
    url: m_serviceURL + "/OAuth/Token",
    data: {
      "grant_type": "client_credentials"
    },
    success: successFunc
  });

  function successFunc(data, status) {
    if (typeof callback == "function") { 		
      callback(data.access_token);
    }
  }
}