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Archive for the 'JavaScript' Category

Jul 12 2008

Using JSON with Prototype

Published by Prajwal Tuladhar under Ajax, JavaScript, PrototypeJS

Ajax stands for Asynchronous Javascript and XML. It is an amalgamation of both new and old technologies - old because it uses already existing technologies and new because it integrates these existing technologies that few considered previously. Ajax is a technology that complements Web 2.0 and the integration of many web services at once.

Though ‘x’ of Ajax stands for XML, instead of XML another format has been gaining wide acceptance and momentum as a medium for information interchange which is called JSON aka JavaScript Object Notation. JSON is an open format describing how to represent JavaScript objects in a simple text representation that can be easily created and parsed. In other words, one can send data to the browser encoding as JSON objects instead of XML, and the JSON objects can be converted easily into JavaScript objects. Three major advantages of JSON:
1. No manual parsing necessary because JSON itself is an object whereas XML is typeless.
2. JSON frees us from having to parse data. DOM manipulation is not necessary with JSON.
3. The physical size of JSON data is less than that of XML. That is why JSON is also called “Fatless XML”.

XML Data Format

<Students>
<Student>
<Name>Pajwal Tuladhar</Name>
<Faculty>BIM</Falculty>
<GPA>3.52</GPA>
<Age>22</Age>
</Student>
</Students>

.csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, “Courier New”, courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }

JSON Data Format

{<span class="str">"Students"</span>:[
{<span class="str">"Name"</span>:<span class="str">"Prajwal Tuladhar"</span>,<span class="str">"Faculty"</span>:<span class="str">"BIM"</span>,<span class="str">"GPA"</span>:<span class="str">"3.52"</span>,<span class="str">"Age"</span>:<span class="str">"22"</span>},
{<span class="str">"Name"</span>:<span class="str">"Max Payne"</span>,<span class="str">"Faculty"</span>:<span class="str">"MBA"</span>,<span class="str">"GPA"</span>:<span class="str">"3.90"</span>,<span class="str">"Age"</span>:<span class="str">"25"</span>},
{<span class="str">"Name"</span>:<span class="str">"Ada Lovelace"</span>,<span class="str">"Faculty"</span>:<span class="str">"BBA"</span>,<span class="str">"GPA"</span>:3.25,<span class="str">"Age"</span>:22}
]}

Lets Code

Ajax.html file

<span class="kwrd">&lt;!</span><span class="html">DOCTYPE</span> <span class="attr">html</span> <span class="attr">PUBLIC</span> <span class="kwrd">"-//W3C//DTD HTML 4.01 Transitional//EN"</span> <span class="kwrd">"http://www.w3.org/TR/html4/loose.dtd"</span><span class="kwrd">&gt;</span>

<span class="kwrd">&lt;</span><span class="html">html</span><span class="kwrd">&gt;</span>

<span class="kwrd">&lt;</span><span class="html">head</span><span class="kwrd">&gt;</span>

    <span class="kwrd">&lt;</span><span class="html">meta</span> <span class="attr">http-equiv</span><span class="kwrd">="Content-Type"</span> <span class="attr">content</span><span class="kwrd">="text/html; charset=ISO-8859-1"</span><span class="kwrd">&gt;</span>

    <span class="kwrd">&lt;</span><span class="html">title</span><span class="kwrd">&gt;</span>Ajax 2<span class="kwrd">&lt;/</span><span class="html">title</span><span class="kwrd">&gt;</span>

    <span class="kwrd">&lt;</span><span class="html">script</span> <span class="attr">type</span><span class="kwrd">="text/javascript"</span> <span class="attr">src</span><span class="kwrd">="js/prototype.js"</span><span class="kwrd">&gt;&lt;/</span><span class="html">script</span><span class="kwrd">&gt;</span>

    &lt;script type=<span class="str">"text/javascript"</span>&gt;

        window.onload = <span class="kwrd">function</span>()    {

            $(<span class="str">'CmdMakeRequest'</span>).onclick = <span class="kwrd">function</span>()    {

                <span class="kwrd">var</span> uri = <span class="str">"data2.php"</span>;

                <span class="kwrd">new</span> Ajax.Request(uri, {

                    method : <span class="str">"post"</span>,

                    onSuccess : <span class="kwrd">function</span>(t)    {

                        <span class="kwrd">var</span> r = eval(<span class="str">'('</span> + t.responseText +<span class="str">')'</span>);

                        <span class="rem">//alert(r.Students[0].GPA);</span>

                        <span class="kwrd">var</span> e = $(<span class="str">'ResponseContainer'</span>);

                        r.Students.each(<span class="kwrd">function</span>(o)    {

                            <span class="kwrd">var</span> t = document.createElement(<span class="str">'table'</span>);

                            e.appendChild(t);

                            createTableCell(<span class="str">"Name"</span>, o.Name, t);

                            createTableCell(<span class="str">"Faculty"</span>, o.Faculty, t);

                            createTableCell(<span class="str">"GPA"</span>, o.GPA, t);

                            createTableCell(<span class="str">"Age"</span>, o.Age, t);

                            <span class="kwrd">var</span> h = document.createElement(<span class="str">"hr"</span>);

                            e.appendChild(h);

                        });

                    }

                });

            };

        };

        <span class="kwrd">function</span> createTableCell(cellKey, cellValue, t)    {

            <span class="kwrd">var</span> tr = document.createElement(<span class="str">"tr"</span>);

            <span class="kwrd">var</span> tdKey = document.createElement(<span class="str">"td"</span>);

            tdKey.appendChild(document.createTextNode(cellKey));

            tdKey.width = <span class="str">"130px"</span>;

            <span class="kwrd">var</span> tdValue = document.createElement(<span class="str">"td"</span>);

            tdValue.appendChild(document.createTextNode(cellValue));

            tr.appendChild(tdKey);

            tr.appendChild(tdValue);

            t.appendChild(tr);

        }

    <span class="kwrd">&lt;/</span><span class="html">script</span><span class="kwrd">&gt;</span>

    <span class="kwrd">&lt;</span><span class="html">style</span> <span class="attr">type</span><span class="kwrd">="text/cs"</span><span class="kwrd">&gt;</span>

        .request-container    {

            border: 1px solid red;

            padding: 10px;

            margin: 10px;

        }

        input {

            font: 14px;

            font-weight: bold;

        }

    <span class="kwrd">&lt;/</span><span class="html">style</span><span class="kwrd">&gt;</span>

<span class="kwrd">&lt;/</span><span class="html">head</span><span class="kwrd">&gt;</span>

<span class="kwrd">&lt;</span><span class="html">body</span><span class="kwrd">&gt;</span>

    <span class="kwrd">&lt;</span><span class="html">div</span> <span class="attr">class</span><span class="kwrd">="request-container"</span><span class="kwrd">&gt;</span>

        <span class="kwrd">&lt;</span><span class="html">input</span> <span class="attr">type</span><span class="kwrd">="button"</span> <span class="attr">id</span><span class="kwrd">="CmdMakeRequest"</span> <span class="attr">value</span><span class="kwrd">="Make Request"</span> <span class="kwrd">/&gt;</span>

    <span class="kwrd">&lt;/</span><span class="html">div</span><span class="kwrd">&gt;</span>

    <span class="kwrd">&lt;</span><span class="html">div</span> <span class="attr">id</span><span class="kwrd">="ResponseContainer"</span><span class="kwrd">&gt;</span><span class="attr"> </span><span class="kwrd">&lt;/</span><span class="html">div</span><span class="kwrd">&gt;</span>

<span class="kwrd">&lt;/</span><span class="html">body</span><span class="kwrd">&gt;</span>

<span class="kwrd">&lt;/</span><span class="html">html</span><span class="kwrd">&gt;</span>

data.php file

&lt;?php

    header(<span class="str">"Content-type: application/jsonrequest"</span>);

    $json_data = array(

        <span class="str">"Students"</span> =&gt; array(

            array(

                <span class="str">"Name"</span> =&gt; <span class="str">"Prajwal Tuladhar"</span>,

                <span class="str">"Faculty"</span> =&gt; <span class="str">"BIM"</span>,

                <span class="str">"GPA"</span> =&gt; <span class="str">"3.52"</span>,

                <span class="str">"Age"</span> =&gt; <span class="str">"22"</span>

            ),

            array(

                <span class="str">"Name"</span> =&gt; <span class="str">"Max Payne"</span>,

                <span class="str">"Faculty"</span> =&gt; <span class="str">"MBA"</span>,

                <span class="str">"GPA"</span> =&gt; <span class="str">"3.90"</span>,

                <span class="str">"Age"</span> =&gt; <span class="str">"25"</span>

            ),

            array(

                <span class="str">"Name"</span> =&gt; <span class="str">"Ada Lovelace"</span>,

                <span class="str">"Faculty"</span> =&gt; <span class="str">"BBA"</span>,

                <span class="str">"GPA"</span> =&gt; 3.25,

                <span class="str">"Age"</span> =&gt; 22

            )

        )

    );

    echo json_encode($json_data);

?&gt;

I have used json_encode() function to encode json data. It is available from PHP 5 or if you are using PHP 4 you can download it from here. By making simple Ajax.Request Object of prototype you can request JSON data and after evaluating it by using eval keyword it is converted into Javascript Object. I have made table to display the data. But the dynamic DOM generation of table is not working on IE (thatswhy IE sucks). But this is only a simple example of how one can use JSON in this data intensive world of web and make most of it.

json_before

Fig. Before making request

json_after

Fig. After making request

json_response

Fig. JSON Response

json_header

Fig. JSON Header

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Mar 14 2008

Ajax and XML : Ajax for tables

Published by admin under Ajax, JavaScript, PrototypeJS

IBM DeveloperWorks has published a very nice article illustrating the use of Ajax and XML for displaying and/or working with tabular data. Prototype JS framework has been used in the article.

http://www.ibm.com/developerworks/xml/library/x-ajaxxml10/?S_TACT=105AGX54&S_CMP=B0314&ca=dnw-910

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