A small group of functions for handling POST and GET requests so I don't always have to write out the same stuff

ajax.js

(function() {
  function newXHR() {
    if (window.ActiveXObject) {
      try {
        return new ActiveXObject("Microsoft.XMLHTTP");
      } catch (e) {
        console.error(e.message);
        return null;
      }
    }
    
    return new XMLHttpRequest();
  }
  
  function get(url, callback) {
    var xhr = newXHR();
    
    xhr.open("GET", url);
    
    xhr.onload = function() {
      callback.call(xhr);
    };
    
    xhr.send();
  }
  
  function post(url, args, callback) {
    var argString = args,
        xhr = newXHR();
    
    if (args instanceof Object) {
      var keys = Object.keys(args);
      argString = "";
      
      for (var i = 0; i < keys.length; i++) {
        if (argString.length > 0) {
          argString += "&";
        }
        
        argString += encodeURI(keys[i] + "=" + args[keys[i]]);
      }
    }
    
    xhr.open("POST", url);
    xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    
    xhr.onload = function() {
      callback.call(xhr);
    }
    
    xhr.send(argString);
  }
  
  window.ajax = {
    get: get,
    post: post
  }
})();

usage.js

// GET request

ajax.get("http://example.com", function() {
  console.log("Status code: " + this.status);
  console.log("Response text: " + this.responseText);
});

// POST requests

ajax.post("http://example.com", "hello=world&foo=bar", function() {
  console.log("Status code: " + this.status);
  console.log("Response text: " + this.responseText);
});

var args = {
  hello: "world",
  foo: "bar"
}

ajax.post("http://example.com", args, function() {
  console.log("Status code: " + this.status);
  console.log("Response text: " + this.responseText);
});