How do I write the following line which is in javascript in jQuery?

var variablename = new functionname('some variable');

This is my js code: var rt = new ResizeableTextbox('myRT');

I need to use this in the following code segment:

 if($(this).text() =='String')
 {
    $("<label id=labelstr"+stringinc+" >"+label+"</label>").appendTo(".menu li");            
    $("<input id=inputstr"+stringinc+" type= 'text' ></input>").appendTo(".menu li");              
    //in place of this I need that javascript code.
 }

How do I do that? The function Resizeable is defined in a separate js file. Please help me out.