Error when trying to put selected node into a global variable - vis.js network

Question

I'm working with vis.js network in my Angular project.

I have this code to get the selected node, this code is in my ngOnInit():

network.on('click', function (properties) {
  var nodeID = properties.nodes[0];
  var edgeFrom = properties.edges
  if (nodeID) {
    console.log("Selected node id:",nodeID)
    this.selectedNode = nodeID //Error here
  }
});

But I get an error (see code above) "'this' implicitly has type 'any' because it does not have a type annotation".

Can anyone explain how I should approach filling a global variable with this ID?