DC.js - Introduction to D3.js

D3.js is a JavaScript library used to create interactive visualizations in the browser. The D3 library allows us to manipulate elements of a webpage in the context of a dataset. These elements can be HTML, SVG, or Canvas elements, and can be introduced, removed, or edited according to the contents of the dataset. It is a library for manipulating DOM objects. D3.js can be a valuable aid in data exploration. It gives you control over your data's representation and lets you add data interactivity.

D3.js is one of the premier framework when compared to other libraries. This is because; it works on the web and data visualizations and is of enterprise grade. Another reason is its great flexibility, which enables developers around the world to create many advanced charts. Also, it has extended its functionality to a great extent.

Let us understand the basic concepts of D3.js, which are as follows −

  • Selections
  • Data join
  • SVG
  • Transition
  • Animation
  • D3.js API

Let us understand each of these concepts in detail.


Selections is one of the core concept in D3.js. It is based on the CSS Selector concept. Those who have used and are aware of JQuery already can easily understand the selections. It enables us to select the DOM based on CSS selectors and then provide options to modify or append and remove the elements of DOM.

Data Join

Data join is another important concept in D3.js. It works along with selections and enables us to manipulate the HTML document with respect to our dataset (a series of numerical values). By default, D3.js gives dataset the highest priority in its methods and each item in the dataset corresponds to a HTML element.


SVG stands for Scalable Vector Graphics. SVG is an XML based vector graphics format. It provides options to draw different shapes such as Lines, Rectangles, Circles, Ellipses, etc. Hence, designing visualizations with SVG gives you more power and flexibility.


SVG provides options to transform a single SVG shape element or group of SVG elements. SVG transform supports Translate, Scale, Rotate and Skew.


Transition is the process of changing from one state to another of an item. D3.js provides a transition() method to perform transition in the HTML page.


D3.js supports animation through transition. Animation can be done with the proper use of transition. Transitions are a limited form of key frame animation with only two key frames: start and end. The starting key frame is typically the current state of the DOM, and the ending key frame is a set of attributes, styles and other properties you specify. Transitions are well suited for transitioning to a new view without a complicated code that depends on the starting view.

D3.js API

Let us understand some of the important D3.js API's methods in brief.

Collections API

A collection is simply an object that groups multiple elements into a single unit. It is also called as a container. It contains Objects, Maps, Sets and Nests.

Paths API

Paths are used to draw rectangles, circles, ellipses, polylines, polygons, straight lines and curves. SVG Paths represent the outline of a shape that can be stroked, filled, used as a clipping path, or any combination of all three.

Axis API

D3.js provides functions to draw axes. An axis is made of lines, ticks and labels. An axis uses scale, thus each axis will need to be given a scale to work with.

Zooming API

Zooming helps to scale your content. You can focus on a particular region using the click-and-drag approach.

Delimiter-Separated Values API

A delimiter is a sequence of one or more characters used to specify the boundary between separate, independent regions in plain text or other data. A field delimiter is a sequence of comma-separated values. In short, the delimiter-separated values are Comma-Separated Values (CSV) or Tab-Separated Values (TSV).