test.html

<!DOCTYPE html>
<html>
  <head>
    <title>treehugger.js demo</title>
    <script data-main="lib/demo" src="lib/require.js"></script>
    <style>
    textarea {
      font-family: "Courier new";
      font-size: 11pt;
      width: 100%;
      height: 100%;
    }
    table {
      width: 100%;
      border: 0;
    }
    </style>
  </head>
  <body>
  <h1>Treehugger.js playground</h1>
    <table>
    <tr>
      <th>Javascript</th>
      <th>AST</th>
    </tr>
    <tr>
      <td><textarea id="code" rows="15" cols="42">var a = 10, b;
console.log(a, b, c);</textarea></td>
      <td><textarea id="ast" rows="15" cols="42" readonly style="background-color: #eee;"></textarea></td>
    </tr>
    <tr>
      <th>Analysis code <button id="runbutton">Run</button></th>
      <th>Output</th>
    </tr>
    <tr>
      <td><textarea id="analysis" rows="15" cols="42">var declared = {console: true};

ast.traverseTopDown(
   'VarDecl(x)', function(b) {
      declared[b.x.value] = true;
   },
   'VarDeclInit(x, _)', function(b) {
      declared[b.x.value] = true;
   },
   'Var(x)', function(b) {
      if(!declared[b.x.value])
        log("Variable " + b.x.value + " is not declared.");
   }
);
</textarea></td>
      <td><textarea id="output" rows="15" cols="42" readonly style="background-color: #eee;"></textarea></td>
    </tr>
    </table>
  </body>
</html>