Question

the jquery function “.textAnim” does nothing
textTyping_animation(); Works fine, but .textAnim doesn’t work.
Here is the plugin code:

function textTyping_animation(text,location,speed){
var progress = 0;
var a = setInterval(function(){
    progress++;
    document.getElementById(location).innerHTML = text.substring(0,progress);
    if(progress == text.length){
        clearInterval(a);
    }
},speed);
};
(function($){
$.fn.textAnim = function(text,speed){
    var progress = 0;
    var a = setInterval(function(){
        progress++;
        $(this).html(text.substring(0,progress));
        if(progress == text.length){
            clearInterval(a);
        }
    },speed);
};
})(jQuery);

Here is the execution:

$(document).ready(function(){
starttext = function()
{
    document.getElementById("textbox").style.display = "block";
    //textTyping_animation("Dit is een dummy text!","textbox_inner",70);
        $("#textbox_inner").textAnim("Dit is een dummy text!",70);
}
});

Html load code:

<script type="text/javascript" language="javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js" ></script>
<script type="text/javascript" language="javascript" src="js/jqueryplugins.js" ></script>
<script type="text/javascript" language="javascript" src="js/libraries/gamelibrary.js"></script>

Answer 1

The problem is that this inside the callback function passed to setInterval() is the window, not the element you want it to be. Modify your code to save a reference to this inside the textAnim() function (which does refer to the correct element), then use that inside the callback passed to setInterval():

(function($){
    $.fn.textAnim = function(text,speed){
        var progress = 0,
            element = this; // this will be the element in the jQuery object
        var a = setInterval(function(){
            progress++;
            $(element).html(text.substring(0,progress));
            if(progress == text.length){
                clearInterval(a);
            }
        },speed);
    };
})(jQuery);

Here’s an updated DEMO.