CODE EXAMPLE FOR JAVASCRIPT

activate treeview menu in adminlte 3.0.2 treeview-menu open

/** add active class and stay opened when selected */
  var url = window.location;

// for sidebar menu entirely but not cover treeview
  $('ul.nav-sidebar a').filter(function() {
    return this.href == url;
  }).addClass('active');

// for treeview
  $('ul.nav-treeview a').filter(function() {
    return this.href == url;
  }).parentsUntil(".nav-sidebar > .nav-treeview").addClass('menu-open').prev('a').addClass('active');