How to check if object within object exists

Question

It seems that the following technique for checking the existence of an object member produces an error because the \'bar\' parent object hasn\'t been declared before the che

Answer 1

You could wrap it up into a method:

function checkGraph(obj, graphPath)
{
  var parts = graphPath.split(".");
  var root = obj;

  for (var i = 0; i < parts.length; i++)
  {
    var part = parts[i];
    if (root[part] && root.hasOwnProperty(part))
      root = root[part];
    else
      return false;
  }

  return true;
}

Where you could call it as:

var foo = {},
    newVal = checkGraph(foo, "bar.myVal") ? foo.bar.myVal : null;