This project is part of udacity professional web track course.

downloading sekeleton containing html and css file

adding some fuctionality using javascript : -building navigation dynamically -work with events to specify active sections -link navigation items to thier corresponding section

using .querySelectorALL() to select all sections then loop to make new corresponding <li> element using document.createElement() then append the created element to the navigation <ul> note use document.createDocumentFragment() for better performance.

use .getBoundingClientRect() to get bounds of the every section element and if it is top bound is between 0 and 300 remove active class from every all sections then add the active class to that section using classList.add()