我需要的是通過javascript重建prototype.js Ajax請求。（沒有 jQuery / 沒有獲?。?。需要 IE 支持（出于某些原因...）new Ajax.Request(urlVar,{  method: 'post',  parameters: {elid: document.getElementById('element').selectedIndex},  onCreate: function(){    //do somethings  },  onComplete: fucnction (event){    currentValues = eval('(' + event.responseText + ')');    console.log(currentValues); // will give me an array with 3 objects  }});我嘗試過的是：var xhr = new XMLHttpRequest();xhr.open("POST", urlVar, true);xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");xhr.onreadystatechange = function (event) {   if (xhr.readyState == 4) {      if (xhr.status == 200) {         currentValues = eval('(' + event.responseText + ')');         console.log(currentValues); // i see an error that "currentValues" is undefined         //i can get 1 object if i will do eval('(' + THIS.responseText + ')');         // but it still bugs me a lot..         //other actions here      }      else if (xhr.status == 400) {         console.log('ERROR')      }      else {         console.log('something else other than 200 was returned');      }   }}xhr.send(document.getElementById('element').selectedIndex);也許有人知道在這種情況下哪種結構會起作用。有什么方法可以通過 js 執行 onCreate / onComplete 嗎？