skill-assessment-app/app/assets/javascripts/live-coder/editor.js.erb

function updateResults(elem) {
  if ($(elem).length ===0){return false;}

  var resultsContainer = $(elem).find('[data-id="results"]')[0];
  var codeHtml = $(elem).find('.code-html')[0].value.trim();
  var codeCss = $(elem).find('.code-css')[0].value.trim();
  var codeJs = $(elem).find('.code-js')[0].value.trim();

  resultsContainer.innerHTML = "";
  var iDoc = document.createElement('html');
  var iHead = document.createElement('head');
  var iBody = document.createElement('body');

  var codeFrame = document.createElement('iframe');
  codeFrame.setAttribute("width", "100%");
  codeFrame.setAttribute("height", "100%");
  resultsContainer.appendChild(codeFrame);

  var jqueryNode = document.createElement("script");
  jqueryNode.setAttribute("type", "text/javascript");
  jqueryNode.setAttribute("src", "<%= "//#{ENV['full_app_url']}#{javascript_path "jquery"}" %>");
  iHead.appendChild(jqueryNode);

  var codeStyle = document.createElement("style");
  codeStyle.setAttribute("type", "text/css");
  var rulesNode = document.createTextNode(codeCss);
  codeStyle.appendChild(rulesNode);
  iHead.appendChild(codeStyle);

  iDoc.appendChild(iHead);
  iBody.innerHTML = codeHtml;
  iDoc.appendChild(iBody);

  var codeScript = document.createElement("script");
  codeScript.setAttribute("type", "text/javascript");
  var scriptNode = document.createTextNode("setTimeout(function(){ " + codeJs + "}, 800);");
  codeScript.appendChild(scriptNode);
  iDoc.appendChild(codeScript);

  codeFrame.contentWindow.document.open();
  codeFrame.contentWindow.document.appendChild(iDoc);
  codeFrame.contentWindow.document.close();
}

function indentSelection(e){
  if(e.keyCode === 9){
    e.preventDefault();

    var indent = "  ";
    var cursor = e.target.selectionStart;
    var val = e.target.value;
    var valStart = val.substring(0, e.target.selectionStart);
    var valEnd = val.substring(e.target.selectionEnd, val.length);
    var selected = val.substring(e.target.selectionStart, e.target.selectionEnd);

    var resetCursor = function(start, end){
      e.target.selectionStart = start;
      e.target.selectionEnd = end;
    };

    var indented;
    if(e.shiftKey){ //de-indent
      if(selected.length > 0 && (/\n/.test(selected))){ //multi line
        indented = selected.split(/\n/).map(function(line){
          if(line.length > 0 && line.substring(0, indent.length) === indent){
            line = line.substring(indent.length, line.length);
          }
          return line;
        }).join("\n");
        e.target.value = valStart + indented + val.substring(e.target.selectionEnd, val.length);
        resetCursor(cursor, cursor + indented.length);
      } else {
        if(valStart.substring(valStart.length - indent.length) === indent){
          e.target.value = valStart.substring(0, valStart.length - indent.length) + valEnd;
          resetCursor(cursor, cursor - indent.length);
        } else if(valEnd.substring(0, indent.length) === indent) {
          e.target.value = valStart + valEnd.substring(indent.length, valEnd.length);
          resetCursor(cursor, cursor);
        }
      }
    } else { //indent
      if(selected.length > 0 && (/\n/.test(selected))){ //multi line
        indented = selected.split(/\n/).map(function(line){
          if(line.length > 0){ line = indent + line; }
          return line;
        }).join("\n");
        e.target.value = valStart + indented + val.substring(e.target.selectionEnd, val.length);
        resetCursor(cursor, cursor + indented.length);
      } else {
        e.target.value = valStart + indent + selected + valEnd;
        resetCursor(cursor + indent.length, cursor + indent.length);
      }
    }
  }
}


var timer = 0;
$(function(){
  // wait a half second before updating results
  // restart the timer if they resume typing
  $('html').on('keyup', '.code-input textarea', function(){
    var elem = $(this).closest("[data-id=live-coder-answer]");
    if (timer) { clearTimeout(timer); }
    timer = setTimeout(updateResults(elem), 500);
  });

  $("[data-id=live-coder-answer]").each(function(){
    updateResults(this);
  });

  $("html").on('keydown', "textarea[data-id^=code-]", function(e){
    indentSelection(e);
  });

  $(".code-input textarea").linedtextarea();
});