jQuery

• 26.1 Prefix jQuery object variables with a $.

  // bad
  const sidebar = $('.sidebar');
  // good
  const $sidebar = $('.sidebar');
  // good
  const $sidebarBtn = $('.sidebar-btn');

• 26.2 Cache jQuery lookups.

  // bad
  function setSidebar() {
    $('.sidebar').hide();
    // ...
    $('.sidebar').css({
      'background-color': 'pink',
    });
  }
  // good
  function setSidebar() {
    const $sidebar = $('.sidebar');
    $sidebar.hide();
    // ...
    $sidebar.css({
      'background-color': 'pink',
    });
  }

• 26.3 For DOM queries use Cascading $('.sidebar ul') or parent > child $('.sidebar > ul'). jsPerf

• 26.4 Use find with scoped jQuery object queries.

  // bad
  $('ul', '.sidebar').hide();
  // bad
  $('.sidebar').find('ul').hide();
  // good
  $('.sidebar ul').hide();
  // good
  $('.sidebar > ul').hide();
  // good
  $sidebar.find('ul').hide();