ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

How to Create an Ajax TreeView in Html

Updated on July 27, 2011



This example uses the HttpRequest to get data from a back end source (database) and generate an Ajax enabled Tree View.


The most important part of the AJAX functionality is the code to connect with your back end system that allows asynchronous communication without having to do any screen refresh. We al know this as Ajax. The XmlHttpRequest, althought implemented differently in the major browsers, it performs is the keystone function which allows this type of communication. The function allows the client to communicate with the back-end (php, ruby, python, java, .net, you name it) without any screen refresh, and I might add, also you a user to continue working while the data is being fetched form the server.

Lets take a look at the code; first setup a variable to hold the XmlHttpRequest object, next the function, GetDocListingsReq, which takes a url param that points to your back end system, then create an XmlHttpRequest object that the HttpRequest will respond to. The onreadystatechange is an event that is triggered every time the state changes and declares what function to call every time the state changes. The other Http variables establish the of Http operations; Post or Get, the header variable also gets the url to act on and sends the command to open the url.

As the state changes, the GetDocListingResp function is called, which checks the status of the Http request; a ReadyState = 4 means the request is finished and the response is ready for the return journey to the calling client; the http.status=200 means that everything is ok. These operations must be checked each time an Ajax operation is performed that has an operation on the server.

Once the status = 200 is received, the response text can be assigned to a variable and the receiving html element can be established to received the response text. In our example it is a div element which receives the http response text.


var httpreq=null;
function GetDocListingsReq(url)
{
//Firefoc, Chrome, Safari or Opera
if (window.XMLHttpRequest) {
httpreq= new window.XMLHttpRequest;
}
else {
try {
//Microsoft
httpreq= new ActiveXObject("MSXML2.XMLHTTP.3.0");
}
catch(ex) {
try{
//Old version of Microsoft, IE 6 and earlier
httpreq= new ActiveXObject("Microsoft.XMLHTTP");
}catch(e)
{

alert("Unable to retrieve documents");

return false;
}

}
}
httpreq.onreadystatechange = GetDocListingResp;
httpreq.open('POST', url, true);
httpreq.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
httpreq.setRequestHeader("Connection", "close");
httpreq.send();

}

function GetDocListingResp() {

if (httpreq.readyState == 4) {
if (httpreq.status == 200) {
result = httpreq.responseText;

document.getElementById('docListings').innerHTML = result; 

} else {
alert('There was a problem with the request.');
}


}
}

The Http response must have the following format for this TreeView design to work
<div id=’category’+RandomNumber onClick=”expandCollapse(this)”>
<div id=’subdcat’+randomNumber onClick=”expandCollapse(this)”>Some Text</div>

<div id=’subdcat’+randomNumber onClick=”expandCollapse(this)”>Another leaf</div>

</div>

This function is called when a user clicks on a div node. Depending on the id that is passed to the function, either the top leaf is hidden or unhidden, or one of the sub category div elements. The trunk variable is assigned the top div element and when clicked, hides the leafs or child nodes under it.

function expandCollapse(divid)
{

var divid_str = divid.id;
var divid_sstr =divid_str.substr(0, 8);

var divid_hex = divid.id.substr( 8, divid.id.length);

switch(divid_sstr)
{
case 'category':

var trunk = document.getElementById(divid_str);
var leaf=document.getElementById('subdcats'+divid_hex);


trunk.style.cursor = 'pointer';
leaf.style.cursor = 'pointer';
trunk.onclick = function() {
if( leaf.style.display == 'none')
{

leaf.style.display = 'block';
}else
{

leaf.style.display = 'none';
}
}
break;
case 'subdcats':
var trunk = document.getElementById(divid_str);
var leaf=document.getElementById('subdcats'+divid_hex);


trunk.style.cursor = 'pointer';
leaf.style.cursor = 'pointer';
trunk.onclick = function() {
if( leaf.style.display == 'none')
{

leaf.style.display = 'block';
}else
{

leaf.style.display = 'none';
}
}

break;

}

}

function GetXMLViewData() {
GetDocListingsReq('http://urlToOpenâ);
}

The GetXMLViewData function is called thrugh the body onload event. The nested div elements can have as many nodes as desired. You just need to add more case branch to the expandCollapse function.

Comments

    0 of 8192 characters used
    Post Comment

    • klanguedoc profile imageAUTHOR

      Kevin Languedoc 

      6 years ago from Canada

      Hi Ruby

      Thanks for the feedback. Yes, indeed, programming is a very creative field and you are only limited by your imagination.

    • Ruby H Rose profile image

      Maree Michael Martin 

      6 years ago from Northwest Washington on an Island

      Way over my head, but I enjoy reading about such inside workings of these fantastic ways of working with our computers. I can admire how well it is written, and part of my brain wants to understand. Thanks for some great hubs!

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)