D3.Javascript also known as Data-Driven Documents is the library function that produces dynamic and interactive data, provides flexibilty of the visualization, such as charts, maps in the web browsers. D3.js itself is data-driven, that gets its super power from data. D3 supports all types of Data like XML , CSV , arrays and many more. The data can be directly fetch from a local file in your working directory. It makes uses of

1. Scalable Vector Graphics (SVG)
2. HTML5
3. Cascading Style Sheets (CSS) standards.

Why Do We Need D3.js?

D3.js is one of the premier framework when compare to other libraries. This is because it works on the web and its data visualizations are par excellence. Another reason it has worked so well is owing to its flexibility. Since it works seamlessly with the existing web technologies and can manipulate any part of the document object model, it is as flexible as the Client Side Web Technology Stack (HTML, CSS, and SVG). It has a great community support and is easier to learn. Unlike many other data visualization libraries that provide ready made charts, D3 gives you lots of freedom to be creative, as you have total control over the visualizations you create since its a user friendly.

In addition to the fact that D3 uses these familiar technologies, it has several other benefits:

1. It is good for creating visualizations with appealing interactions.
2. It encourages code reusability.
3. D3 is extremely fast.
4. It supports large datasets and provides an easy way of loading and transforming data. 5.Has wide variety of curve generating functions. 6.Associates data to an element or group of elements in the HTML page.

How to Select Elements in D3:

While working on code if you want to modify elements on your page you can do it by selecting the particular element . D3.js works the same way, and provides us with two methods to select DOM elements:

(i) d3.select() (ii) d3.selectAll() Both of this selector methods will take in any CSS selector and return the element that matches the specified selector. If no element matches the selector it will return an empty selection.

(i) d3.select : The d3.select() method will target the element which appears first and also matches int DOM(from top to bottom). If there are multiple elements that matches the condition and specified selector d3.select() will match the one that is on top.

d3.select("#d3_p").style("color" , "white");


output:
Hello welcome 1
//Hello welcome 2
//Hello welcome 3
//Hello welcome 4

In the above ouput the one which is on top "Hello world 1" is selected and targeted .

(ii)d3.selectAll() : The d3.selectAll() method works and functions almost similar to d3.select() but unlike it, it targets and selects all the elements that are matchid in the selector.

d3.selectAll(".d3_p").style("color","white");


output:

Hello welcome 1
Hello welcome 2
Hello welcome 3
Hello welcome 4

Here are certain ways to modify elements in D3: After selecting your DOM elements you can modify them-

--> .attr() : update the selected element attribute

d3.select("z").attr("name" , "Iliyan")

--> .text() : Updates the selected element text content

d3.select('h1').text(' Introduction to d3.js')

--> .style() : Updates the styling property of the element

d3.select("p").style("color" , "Blue");

--> .remove() : Removes the selected element in DOM

d3.select("div").remove("p")

D3.js Benefits D3.js is an open source project and works without any plugin. It requires very less code and comes up with the following benefits −

1.Great data visualization.

2.It is modular. You can download a small piece of D3.js, which you want to use. No need to load the whole library every time.

3.Easy to build a charting component.

4.DOM manipulation

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