In javascript, how do I open a dialog so that the user can input the value of a variable?

Question

I'm working on a script that will be used for many images, all of them using the same format (size of the image, layer layout, etc).
All of these images will have a layer of text, and what I want is to have the script modify the horizontal length of the text layer (horizontal percentage scale), shrinking it so that all of the text appears on-screen, in case there's too much of it.
But the text will vary from image to image, and what I want is for the script to display a dialog box were the user can input the text that will be put on the text layer and scaled down.
Can this be done?

Answer 1

If you want the user to both enter then fit the text while your script is running, here is one way to do that.
var typeLayer = activeDocument.activeLayer;
var type = typeLayer.textItem;
var t = prompt ("Enter text" , "new text");
type.contents= t;
transformLayer();
function transformLayer() {
     try{
     var desc = new ActionDescriptor();
        var ref = new ActionReference();
        ref.putEnumerated( charIDToTypeID('Lyr '), charIDToTypeID('Ordn'), charIDToTypeID('Trgt') );
    desc.putReference( charIDToTypeID('null'), ref );
    desc.putEnumerated( charIDToTypeID('FTcs'), charIDToTypeID('QCSt'), charIDToTypeID('Qcsa') );
        var desc1 = new ActionDescriptor();
        desc1.putUnitDouble( charIDToTypeID('Hrzn'), charIDToTypeID('#Rlt'), 0.000000 );
        desc1.putUnitDouble( charIDToTypeID('Vrtc'), charIDToTypeID('#Rlt'), 0.000000 );
    desc.putObject( charIDToTypeID('Ofst'), charIDToTypeID('Ofst'), desc1 );
    desc.putUnitDouble( charIDToTypeID('Wdth'), charIDToTypeID('#Prc'), 100 );
    desc.putUnitDouble( charIDToTypeID('Hght'), charIDToTypeID('#Prc'), 100 );
    desc.putBoolean( charIDToTypeID('Lnkd'), true );
    executeAction( charIDToTypeID('Trnf'), desc, DialogModes.ALL );
     }catch(e){}