D3.js interview questions

D3 stands for Data-Driven Documents

Mike Bostock wrote D3.js based on his work during his Ph.D. studies at the Stanford Visualization Group. Mike worked at the The New York Times for a while and is now independently working on D3.js.

You can use D3 js because

• D3.js lets you to build the data visualization framework
• D3.js focuses on binding data to DOM elements.
• D3.js is written in JavaScript and uses a functional style which means you can reuse code and add specific functions to your heart’s content.

D3.js uses CSS-style selectors to identify elements on which to operate.
Example:

d3.selectAll("p").style("color", "white");

D3 implements a declarative approach, operating on arbitrary sets of nodes called selections.
Also, Read Neo4j interview questions

In D3.js “Enter” selection is used to create new nodes for incoming data and “Exit” selection is used eliminate outgoing nodes that are no longer required.

There are 7 types of slider are available in D3.js, they are

• Default slider
• Slider with start value
• Slider with slide event: 0
• Slider with default axis
• Slider with custom axis
• Slider with min, max and step values
• Vertical slider

A transition is a selection-like interface for animating changes to the DOM. Instead of applying changes instantaneously, transitions smoothly interpolate the DOM from its current state to the desired target state over a given duration.

To apply a transition, select elements, call selection.transition and then make the desired changes.

For example:

d3.select("body")
  .transition()
    .style("background-color", "red");

d3.interpolateObject(a,b) command is used to interpolate two objects in d3.js

To create scales showing the linear relationship between the output and input we use d3.scale.linear() and d3.scaleLinear(). The domain and range of the scale are set by default at the interval (0,1) which expresses the function y = x. It can be used for flipped range, nice bounds, round ranges, non-numerical range, camping, etc.

There is a minor difference between d3.scale.linear() and d3.scaleLinear() which is on the basis of its use.

• If you want to create d3.js linear scale on version 3 then use API d3.scale.linear()
• If you want to create d3.js linear scale on version 4 and 5 then use API d3.scaleLinear()