AJAX (Asynchronous JavaScript and XML) doesn't relate 100 percent to D3. It actually has its foundation in JavaScript. In short, AJAX allows the developer to obtain data from the background of the web page. This technique is extremely useful in map development because geographic datasets can be very large. Acquiring the data from the background will help produce a refined user experience. In addition, in Chapter 6, Finding and Working with Geographic Data, we will cover techniques to compress the size of geographic data.
Separating the data from the code base will also provide the following advantages:
A lighter code base that is easier to manage
The ability to update the data without making code changes
The ability to use third-party providers for data sources
This is accomplished by acquiring the data through an AJAX call with the aid of a D3 function. Let's examine the following code:
d3.json("data/dataFile.json", function(error, json) {The d3.json method has two parameters: a path to...