onfilter

Object	Explanation
function	Fires a function on keyup when filter text is changed

Parameters	Type	Explanation
this	Object	Treebeard object with its public methods (API)
filterText	String	The value of the filtertext input box

###Example:

var options ={
    ...
    onfilter : function(filterText){
        // this == Treebeard object with access to public methods (API). 
        if(filterText === " "){
            alert("Please enter a valid String");
        } 
        else {
            console.log("on filter: this", this, 'filterText', filterText);
        }
    },
    ...
}