JavaScripting InDesign

I found the documentation for drop-down lists to be less easy to follow than for simpler objects. The script ended up being a lot simpler than I was at first led to believe by the combination of scant information in the Tools Guide and the structure of the object model. Here's what I ended up with:

//DESCRIPTION: Simple ScriptUI Drop-down List

listStrings = ["25%", "50%", "75%", "90%", "100%", "110%", "125%", "140%", "200%", "400%"];
myDlg = new Window('dialog', 'Drop-down List');
myDlg.orientation = 'column';
myDlg.alignment = 'right';
//add drop-down
myDlg.DDgroup = myDlg.add('group');
myDlg.DDgroup.orientation = 'row';
myDlg.DDgroup.add('statictext', undefined, "Zoom Percentage");
myDlg.DDgroup.DD = myDlg.DDgroup.add('dropdownlist', undefined, undefined, {items:listStrings})
myDlg.DDgroup.DD.selection = 4;
myDlg.closeBtn = myDlg.add('button', undefined, 'OK');
// add button functions
myDlg.closeBtn.onClick = function() {
 this.parent.close();
}
result = myDlg.show();
alert(myDlg.DDgroup.DD.selection);

I had the following difficulties:

1. I didn't know how many undefineds to include in the add statement for the list. I arrived at two by trial and error. I imagine that the first one is for the dimension information. I'm not sure what the second one is.
2. I expected to have to create an array of listItems for the items property of the drop-down, but the array of strings sufficed.
3. I went through a number of hoops trying to work out how to set the initial value of the selection before stumbling on the simple use of the index to 100%.
4. As a result of that, I was amazed to discover that the selection returns the selected value and not the index into the list.