Before reading -<p>Wait, how they are going to modernise something that is working well?<p>What do they mean by modernise?<p>Is the modernise technique really better ?<p>First read - There is really no modernisation done and no improvements at all until I saw the chart.<p>Second read - Very carefully trying to understand and found that they removed legacy technique to access a node and replaced it with a node with four pointers - parent, first-child, next, and previous sibling.<p>Its a neat work because trying to migrate a older technique to newer ones will require deeper knowledge !