Bind data to all p elements in the DOM, even if they don’t exist yet.

    d3.select("body") // Find body, pass reference to next step in chain.
        .selectAll("p") // Selects all p in DOM. Returns empty selection. 
        .data(mydata) // Parse and count data. Following methods called n times.
        .enter() // Creates n new placeholder elements apparently.
        .append("p") // Swap placeholder for p element.
        .text("Hello World"); // Insert text value to p.