Paragraph align text with Expressions

Maybe not exactly OP's question, but the answer to my problem was in this link. Explaining here in case anyone comes across this thread in the future.

I was building a mogrt and needed to be able to change the justification of a text box while keeping all the rest of the style properties.

From the helpdoc:

// To return the values of both the style and the actual Source Text at time (short hand)  
var sourceTextProperty = thisComp.layer("MAIN TEXT").text.sourceText; 
var newStyle = sourceTextProperty.getStyleAt(0,0);  
newStyle.setText(sourceTextProperty);

I made 4 duplicates of my text layer (left, right, center, and justify all justifications), and chose the centered layer as my control. I manually set the left and right layers to left and right justification and copied this expression into the source text for the left, right, and all layers:

// To return the values of both the style and the actual Source Text at time (short hand)
var sourceTextProperty = thisComp.layer("Body Copy_Center").text.sourceText;
var newStyle = sourceTextProperty.getStyleAt(0,0);
newStyle.setText(sourceTextProperty);

Then I added a dropdown control to a null, and wrote a quick if/else on the opacity of each layer to turn them on or off depending on which justification the end user wants. That's the control I put in the final mogrt.

For the left align layer it looks like this (where "1" is the dropdown menu option for left align):

align = thisComp.layer("Controls").effect("Body Justification")("Menu");

if(align == 1){100}
else{0};

Hope this helps someone!