<script>
function start() {
  var weak1 = { a: 2 }, weak2 = { a: 5 };

  var set = new Set([{a: 1}]);
  var weakset = new WeakSet([weak1]);
  var map = new Map([[{a: 3},{a:4}]]);
  var weakmap = new WeakMap([[weak2,{a:6}]]);
  debugger;
}
</script>
