Website interface in JavaScript (design needed and autocomplete function in a textarea)

I am looking to have a website interface developed in JavaScript. The primary goal of this interface is to showcase a product or service, and I would like it to have a minimalist design. For the autocomplete feature, I am looking for keyword-based suggestions. This feature should be able to predict what the user is searching for based on the initials they enter. The suggestions should be taken from a jsonfile. Every word should be sort of like a tag or put into a <span> and you should be able to click on the word and add it to the json file.

Most of the coding is done. I only need to fix the autocomplete function and update the design.