Check out example codes for "html tag convert to d3.select() point". It will help you in understanding the concepts better.

Code Example 1

//Class
d3.select(“.classname”)

//Unique identifier
d3.select(“#line”)
          
//Attribute
d3.select(“[color=black]”)

Code Example 2

var selection = d3.select(domElement);

// later via the selection you can retrieve the element with .node()
var elt = selection.node();

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