Simple JavaScript HTTP Client. Supports GET and POST.

HttpClient.js

httpClient = {
	get: function( url, data, callback ) {
		var xhr = new XMLHttpRequest();
		
		xhr.onreadystatechange = function () {
			var readyState = xhr.readyState;

			if (readyState == 4) {
				callback(xhr);
			}
		};
		
		var queryString = '';
		if (typeof data === 'object') {
			for (var propertyName in data) {
				queryString += (queryString.length === 0 ? '' : '&') + propertyName + '=' + encodeURIComponent(data[propertyName]);
			}
		}
		
		if (queryString.length !== 0) {
			url += (url.indexOf('?') === -1 ? '?' : '&') + queryString;
		}
		
		xhr.open('GET', url, true);
		xhr.send(null);
	},
	
	post: function( url, data, callback ) {
		var xhr = new XMLHttpRequest();
		
		xhr.onreadystatechange = function () {
			var readyState = xhr.readyState;

			if (readyState == 4) {
				callback(xhr);
			}
		};
		
		var queryString = '';
		if (typeof data === 'object') {
			for (var propertyName in data) {
				queryString += (queryString.length === 0 ? '' : '&') + propertyName + '=' + encodeURIComponent(data[propertyName]);
			}
		}
		
		xhr.open('POST', url, true);
		xhr.setRequestHeader('content-type', 'application/x-www-form-urlencoded');
		xhr.send(queryString);
	}
};

HttpClientExample.js

// Get all gists for user 'randyburden' and output the Url and Description of each gist to the JavaScript console
httpClient.get( 'https://api.github.com/users/randyburden/gists', null, function(xhr) {
  //console.log( JSON.parse( xhr.responseText ) );
  var gists = JSON.parse( xhr.responseText );
  var list = [];
  for( var i = 0; i < gists.length; i++ ) {
    list.push( { Url: gists[i].html_url, Description: gists[i].description } );
  }
  console.log( list );
});