Illustrator Scripting :: Change Color And Line Weight

I am trying to create a script who could act as an Autocad plot (ie convert each color to black, with a different line weight). 
 
Here is the first script I melted, who create my Black swatch

if ( app.documents.length > 0 ) {
var myDoc = app.activeDocument;
//add Black swatch
var newSwatch = app.activeDocument.swatches.add()
var newColor = new GrayColor();
newColor.gray = 100;
[Code] ......... 
 
And here is the second one, who replace one color by Black (it don't change the text, nor the lineweight yet…
 
if ( app.documents.length > 0 ) {
//test de dialogue
function csDialog() {
var fabGroup = app.activeDocument.swatchGroups.getByName('Fabrics');
var allFabs = fabGroup.getAllSwatches();
var fabNames = Array();

[Code] ........