unwinder-output.js

// This function:

function foo() {
  var x = 5;
  var y = 6;
  debugger;
  return x + y;
}

// Would be compiled to this function. Yes, it's a large transform,
// but it works surprisingly well even if the output JS is very large.
// Also, I hand-wrote the following code (to simplify it) so there
// might be minor errors. Take it as specific pseudo-code.

function foo() {
  var $__next = 0, x, y;

  try {
    if(VM.doRestore) {
      var $__frame = VM.popFrame();
      $__next = $__frame.next;
      var $__child = $__frame.child;

      if($__child) {
        $__frame.state.$__t1 = $__child.fn.call($__child.thisPtr);
      }

      x = $__frame.state.x;
      y = $__frame.state.y;
    }

    while(1) {
      if (VM.breakpoints[1][$__next] !== undefined)
        throw new $ContinuationExc();

      switch($__next) {
        case 0:
          x = 5;
          $__next = 1;
          break;
        case 1:
          y = 6;
          $__next = 2;
          break;
        case 2:
          $__next = 3;
          throw new $ContinuationExc();
        case 3:
          return x + y;
      }
    }
  }
  catch(e) {
    if(!(e instanceof $ContinuationExc))
      e = new $ContinuationExc({ error: e })
    e.pushFrame(new $Frame($__next, { x: x, y: y }));
    throw e;
  }
}