JSX function for Adobe Illustrator to group layers based on a matching substring in the layer names. See code comment for more details.

Group-Layers-in-Adobe-Illustrator.js

/**
 * Group layers in Adobe Illustrator into sub-layers based on a substring 
 * of the layer names. For instance, given layers named with the pattern:
 *    'Icon-set-01-some-keywords-here'
 * Call:
 *   groupLayers('Icon-set-01');
 *    
 * The result will be to create a new parent layer named 'Icon-Set-01' and
 * to group any layer whose name starts with 'Icon-Set-01' under that layer.
 * @param nameStem
 * @returns null
 */
function groupLayers(nameStem) {

    var doc = app.activeDocument;
    var parent, layer;

    try {
        parent = doc.layers.getByName(nameStem);
    }
    catch(e) {
        parent = doc.layers.add();
        parent.name = nameStem;
    }

    var matches = [];
    try {
        for (var i = 0; i < doc.layers.length; i++) {
            var layer = doc.layers[i];
            if (layer.name.indexOf(nameStem) !== -1) {
                if (layer.name.length > nameStem.length) {
                    matches.push(layer);
                }
            }
        }
        for (var i = 0; i  < matches.length; i++) {
            var layer = matches[i];
            layer.move(parent, ElementPlacement.PLACEATEND);
        }
    }
    catch(e) {alert(e)}
}