graphql pass arg

var numSides = 6;
var numRolls = 3;
var xhr = new XMLHttpRequest();
xhr.responseType = 'json';
xhr.open("POST", "http://localhost:4000/graphql");
xhr.setRequestHeader("Content-Type", "application/json");
xhr.setRequestHeader("Accept", "application/json");
xhr.onload = function () {
  console.log('data returned:', xhr.response);
}
var query = `query getDiexx($numSides:Int!,$numRolls:Int!) {
  getDie(numSides: $numSides) {
  numSides 
  roll(numRolls: $numRolls)
 }
}`;
xhr.send(JSON.stringify({
  query: query,
  variables: {numSides: numSides, numRolls: numRolls},
}));