Javascript fire function from object

I would like to add a path on an svg, from an “object”.
myPath() for the attribute d works fine, but
I want to trigger my function from the object obj, and the obj.action() for d doesn’t work… Why ?

var obj = {
  action: function() {
    myPath();
  }
}

function myPath() {
  return "M 10 10 L 50 10 L 50 90 L 10 90 Z";
}

$("button").on('click', function() {
  // doesn't work... :-(
  $("svg").find("path").attr("d", obj.action());

  // ... but it's working with this :
  //$("svg").find("path").attr("d", myPath());
});
svg {
  width: 100px;
  height: 100px;
  background-color: #C0C0C0;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<button>Click Me</button>
<svg><path /></svg>