Basics

All operations in the library are chained to the d3 instance.
D3 is modularized, so you can only import the modules you need to reduce your build size.

Adding Data

.data() is chained to a selection, and binds it with the data passed in as an argument.
.enter() reconciles the data and elements that data is bound to: it creates any necessary extra elements if there is a mismatch between those and the number of data items via .append().

Chloropleth Maps

Events

Don't use arrow functions for input interactions, the scoping of this in that instance leads to problems.

Key Concepts

It will save you a lot of aggravation, especially when you need to transform data in some way, to set accessor functions for certain data points.

Scales

Scales exist to convert values from whatever domain they originally belong to, to a pixel domain.
scaleLinear() deals with numbers that, well, scale in a linear fashion
scaleTime() works with units of time

Selections

select() selects the element passed into this method as an argument.
selectAll() selects all specified elements.

Time

timeParse() takes a string and converts it into a date object.