Creating content

This is the second in a series of articles about learning Javascript. I am not an expert, specifically I am a competent XTHML and CSS coder looking to pick up new skills. If you can add any insight please feel free to add a comment. This is meant to help people learn.

Jump straight to the example if you like or download the source code

createElement and createTextNode

Using the DOM and Javascript it is possible to add content into your page dynamically when a user performs an action without returning to the server. Using createElement and createTextNode we can add HTML to the page. In this example we will add a paragraph with some text when a user clicks a link. We will use createElement to create p tag. Then createTextNode to add text within the paragraph tag.

The markup

First of all let’s create some markup that we can use to hang our Javascript off.

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<h1>Leaning Javascript - Creating content</h1>
<p><a href="non_js_content.html" id="trigger">Clicking this link will dynamically create content</a></p>
<div id="updateDiv">
    <h2>Update panel</h2>
    <p>A new paragraph will be added in here when the user clicks the link above</p>
</div>

There are two ids here for the Javascript to hook into. The first is “trigger”. This is the link that users will click to add content to the page. The second is “updateDiv”. This is where the generated content will be appended. Note if Javascript is turned off then there is a link to take the user to another page.

The Javascript

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function createContent() {

    // Start by declaring our variables
    var updateDiv; // The div we are putting the new content in
    var trigger; // This is the link that fires the function
    var newParagraph; // The new paragraph tag
    var newText; // The new text

    // Check the browser supports getElementById. If not return.
    if(!document.getElementById) { return; }

    // Find div that holds the content
    updateDiv = document.getElementById("updateDiv");

    // If it isn't there return
    if (!updateDiv) { return;}

    // Find the div with the id example
    trigger = document.getElementById("trigger");

    // If it isn't there return
    if (!trigger) { return;}

    //It is there so do some stuff
    trigger.onclick = function(){
        // Create a new paragraph element
        newParagraph = document.createElement('p');
        // Create some text
        newText = document.createTextNode('This paragraph was dynamically inserted using the DOM');
        // Put the text in the new paragraph element
        newParagraph.appendChild(newText);
        // Append the new paragraph to the update Div
        document.getElementById('updateDiv').appendChild(newParagraph);
        // Disable the link by returning false            
        return false;
    }
}

Hopefully the comments should guide you through this. Basically we look for the updateDiv and trigger ids and then wait for the user to click the link. When the link is clicked the content is created and inserted. We use appendChild to put the newly created paragraph and text into the updateDiv container.

Again I’m using Simon Willison’s [addEvent script][3] to get the function ready when the page is loaded. You can see the code in action in the demonstration or download the source code

Cross-browser friendly

This seems to be very cross browser friendly. I’ve tested it ok in the following:

• Win IE5+
• Win Firefox 1+
• Win Opera 7+
• Win Netscape 7+
• Mac IE5.2
• Mac Safari 2
• Mac Firefox 1+
• Mac Camino 1
• Mac Opera 9