While there are a variety of Javascript libraries available for creating visualizations, the most widely used is D3.js.
D3 stands for Data-Driven Documents, and at the core of D3 is a programming model in which users join data elements to document elements. These are often SVG elements, but D3 can really be used for any kind of data-driven DOM manipulation. I instruct my students on the basics of D3.js as part of the Visual Analytics course which I teach every fall.
I came across this intereseting essay from Moritz Stefaner in which he outlines his perspectve on the recent focus on “storytelling” within the data visualization community. I largely agree with his thesis, especially his point about viewing a visualization designer as an author, one who brings to bear editorial decisions about what data to use, where to focus, and what to exclude. There are degrees of editorialship, but even the most quantitative methods include some degree of human decision.