4):This section gives an introduction to DOM.The Document Object Model is the data representation of the objects that comprise the structure and content of a document on the web.the DOM represents the documents as nodes and objects.The DOM is an object-oriented representation of the web page, which can be modified with a scripting language such as JavaScript.
8):This section gives detail information about loops that how to loop through arrays and how to break and continue loops in javascript.
9):This section is about automated responsive images Markup.It shows how to work and process images in javascript.this is specially helpful in big projects and save tons of times.It shows how to update image markup with srcset and sizes attributes.
10):This section is about troubleshooting,validating and minifying java script.It shows some online tools to debug code like jshint and jslint.It also shows how to install packages in your code editor to automate script linting and minifying.
11)This section gives some additional information about javascript like arrow function and % symbol.
2).This section is about Selecting The DOM e.g selecting elements with getElementByID,by Class name,Html Tag and Querying CSS to select elements etc.It also gives an understanding of nodes.