Help Needed: How children's Objects are created?

[Avinash Devarakonda]

for(var j = 0; j < str.length; j++) {
      var item = str[j];
      var itemLength = item.length - 1;
      var node = index;

      for(var n = 0; n < itemLength; n++) {
        var char = item[n];
        var newNode = node[char];
        newNode = newNode === undefined ? {} : newNode;
        node[char] = newNode;
        node = newNode; // ---> This part i cann't able to understand
      }

[kabir shah]

When node is set to newNode, all nodes after that are going to be nested inside of node to make a tree. Check out this section of my blog post for an example of the tree and see if you can work it out.

[Avinash Devarakonda]

from the general programming perspective node is should set to be an empty object, then why all nodes after that nested inside of node to make a tree.
When I am debugging it with debugger i am only seeing an empty object in node