A memo on how to perform ajax GET with XMLHttpRequest in JavaScript.

If you can use jQuery.ajax(), it’s easy to implement, but when you’re restricted to JavaScript, you need to write it like this:

var makeXMLHttpRequest = function(url) {
  var httpRequest;

  if (window.XMLHttpRequest) {
    // Mozilla, Safari, Chrome, ...
    httpRequest = new XMLHttpRequest();
    if (httpRequest.overrideMimeType) {
      httpRequest.overrideMimeType('text/xml');
    }
  } else if (window.ActiveXObject) {
    // IE
    try {
      httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
      try {
        httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
      } catch (e) {
      }
    }
  }

  if (!httpRequest) {
    // console.log('Cannot create XMLHTTP instance');
    return false;
  }

  httpRequest.onreadystatechange = function() {
    processResponse(httpRequest);
  };
  httpRequest.open('GET', url, true);
  httpRequest.send('');
};

var processResponse = function(httpRequest) {
  if (httpRequest.readyState == 4) {
    if (httpRequest.status == 200) {
      doSomething(httpRequest);
    } else {
      // error
    }
  }
};

That’s all from the Gemba.

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Reference Information

・Getting Started - AJAX | MDN

・XMLHttpRequest の使い方 - WebOS Goodies