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No Paragraphs

There are no paragraphs here, d3 inserts them.

Style Update and Enter Selections Together

There are initially two paragraphs here. After appending to the enter selection, D3 merges the enter selection with the update selection. After doing this we both set the text and apply a violet color to the update selection, which will modify all of the paragraphs - both existing and newly inserted. From D3 Wiki:

The enter selection merges into the update selection when you append or insert. This approach reduces code duplication between enter and update. Rather than applying operators to both the enter and update selection separately, you can now apply them to the update selection after entering the nodes. In the rare case that you want to run operators only on the updating nodes, you can run them on the update selection before entering new nodes.

Style Enter and Update Selections Separately

There are initially two paragraphs here. We style the update and enter selections separately, and set the text on the update selection after we have appended to the enter selection.