Script to add letter spacing, line height controls to the Typekit type tester

typekit.com.js

var $tester         = $('#type-tester'),
    $textarea       = $tester.find("textarea"),
    $letter_spacing = $("<input />", {
      className: 'letter-spacing',
      type: 'text',
      id: "#ls",
      value: "0.00"
    }),
    $ls_div = $("<div />",{
        text: "Tracking",
    }),
    $line_height = $("<input />", {
      className: 'line-height',
      type: 'text',
      id: "#lh",
      value: "1"
    }),
    $lh_div = $("<div />",{
        text: "Leading",
    });


if ($tester.length){
  $('<style type="text/css">#type-tester textarea { text-rendering: optimizeLegibility; }</style>').appendTo('head');
  
  $letter_spacing
    .appendTo($ls_div)
    .bind('keyup', function(){
      $textarea.css('letterSpacing', $(this).val() + 'em');
    });
  $ls_div.prependTo($tester);
  
  $line_height
    .appendTo($lh_div)
    .bind('keyup', function(){
      $textarea.css('lineHeight', $(this).val() + 'em');
    });
  $lh_div.prependTo($tester);
}