在javascript中使用来自回调函数的变量

Question

我正在尝试获取我的获取文本给我的数据我从php中的api生成2个json文件我用我的函数获取它们并且可以将其显示为警报但我想在函数dessin中用它干燥图表（）但我无法获得我的dataid和datanom的值 谢谢你的帮助;）

getText = function(url, callback) // How can I use this callback?
{
  var request = new XMLHttpRequest();
  request.onreadystatechange = function() {
    if (request.readyState == 4 && request.status == 200) {
      callback(request.responseText); // Another callback here
    }
  };
  request.open('GET', url);
  request.send();
}

function mycallback(dataid) { //this is the data that am trying to use in 
  alert(dataid);
}

function mycallbacknom(datanom) {
  var datajsonnom = JSON.parse(datanom);
  alert(datajsonnom);
}
   getText('http://localhost/id.json',mycallback);
   getText('http://localhost/nom.json',mycallbacknom);

function dessin() {
  //var lab = datajsonnom;

  var ctx = document.getElementById("myChart");
  var myChart = new Chart(ctx, {
        type: 'bar',
        data: {
          labels: dataid, //i want to put the dataid here
          datasets: [{
                label: '# of Votes',
                data: data, // and the datanom here