Highlight the full line of code being executed using JS Interpreter

Question

I am using JS Interpreter to parse the code and highlight the line of code being executed, I want something like the below (see the video), where each line is highlighted.

When using the JS Interpreter, I get the below (see the video), where parts of each line get executed, instead I would like one line to be executed at a time ( as shown in the above video).

Here is the code behind the highlighting part of JS interpreter, please take a look at the code in stepButton(), which actually creates the selection.

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS-Interpreter Async Demo</title>
  <link href="style.css" rel="stylesheet" type="text/css">
  <script src="../acorn.js"></script>
  <script src="../interpreter.js"></script>
  <script>
    var myInterpreter;
    function initAlert(interpreter, globalObject) {
      var wrapper = function alert(text) {
        return window.alert(arguments.length ? text : '');
      };
      interpreter.setProperty(globalObject, 'alert',
          interpreter.createNativeFunction(wrapper));
    }

    function parseButton() {
      var code = document.getElementById('code').value;
      myInterpreter = new Interpreter(code, initAlert);
      disable('');
    }

    function stepButton() {
      if (myInterpreter.stateStack.length) {
        var node =
            myInterpreter.stateStack[myInterpreter.stateStack.length - 1].node;
        var start = node.start;
        var end = node.end;
      } else {
        var start = 0;
        var end = 0;
      }
      createSelection(start, end);
      try {
        var ok = myInterpreter.step();
      } finally {
        if (!ok) {
          disable('disabled');
        }
      }
    }

    function runButton() {
      disable('disabled');
      if (myInterpreter.run()) {
        // Async function hit.  There's more code to run.
        // There will be a lot of restarts due to regular expressions in Acorn.
        setTimeout(runButton, 0);
      }
    }

    function disable(disabled) {
      document.getElementById('stepButton').disabled = disabled;
      document.getElementById('runButton').disabled = disabled;
    }

    function createSelection(start, end) {
      var field = document.getElementById('code');
      if (field.createTextRange) {
        var selRange = field.createTextRange();
        selRange.collapse(true);
        selRange.moveStart('character', start);
        selRange.moveEnd('character', end);
        selRange.select();
      } else if (field.setSelectionRange) {
        field.setSelectionRange(start, end);
      } else if (field.selectionStart) {
        field.selectionStart = start;
        field.selectionEnd = end;
      }
      field.focus();
    }
  </script>
</head>
<body>
  <h1>JS-Interpreter Self-interpreter Demo</h1>

  <p>The JS-Interpreter can run itself.  To run the demo you <strong>must</strong>
  first open <a href="../acorn_interpreter.js">acorn_interpreter.js</a>, copy the
  entire file, then paste it at the top of the text area below.</p>

  <p>Click <em>Parse</em>, then click <em>Run</em> once and wait a few seconds.
  Open your browser's console for errors.</p>

  <p><textarea id="code" spellcheck="false">
// DO THIS FIRST!
// PASTE CONTENTS OF acorn_interpreter.js HERE.

var code = [
  "var result = [];",
  "function fibonacci(n, output) {",
  "  var a = 1, b = 1, sum;",
  "  for (var i = 0; i < n; i++) {",
  "    output.push(a);",
  "    sum = a + b;",
  "    a = b;",
  "    b = sum;",
  "  }",
  "}",
  "fibonacci(16, result);",
  "alert(result.join(', '));"
].join('\n');

function initAlert(interpreter, globalObject) {
  var wrapper = function(text) {
    return alert(arguments.length ? text : '');
  };
  interpreter.setProperty(globalObject, 'alert',
      interpreter.createNativeFunction(wrapper));
}

myInterpreter = new Interpreter(code, initAlert);
myInterpreter.REGEXP_MODE = 1;
myInterpreter.run();
</textarea><br>
  <button onclick="parseButton()">Parse</button>
  <button onclick="stepButton()" id="stepButton" disabled="disabled">Step</button>
  <button onclick="runButton()" id="runButton" disabled="disabled">Run</button>
  </p>

  <p>Back to the <a href="../docs.html">JS-Interpreter documentation</a>.</p>
</body>
</html>

Highlight the full line of code being executed using JS Interpreter

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