jstree_custom_sort.js

// for this purpose we used the icon propery of our tree object to identify that it is a file (a folder doesn't have an icon, it uses the default one)

var customTreeSort = function(a, b) {
	if (this.get_node(a).icon === 'jstree-file' && this.get_node(b).icon === 'jstree-file') {
		// organize files
		return this.get_text(a).localeCompare(this.get_text(b));
	} else {
		// files before folders
		if (this.get_node(a).icon === 'jstree-file') {
			return -1;
		}
		if (this.get_node(b).icon === 'jstree-file') {
			return 1;
		}
		// organize folders
		return this.get_text(a).localeCompare(this.get_text(b));
	}
};