Data comes in many forms, and data structures equally so. But as terrifying as arrays and objects might seem at first glance, they are easy to grasp in reality. Data structures are used in all programming languages (and one could even say in natural languages). The ways they are and can be structured vary from language to language, but usually values are put in lists and lists within lists.
Numbers are at the core of programming, not just webprogramming, but all programming. In fact, that computers run on binary code, i.e. zeroes and ones, can be considered common knowledge. But since writing programs in binary is a hell of a job, computer scientists have developed a number of ways to represent numbers.
Read the articles you can find below ("How numbers are encoded" is optional)
Watch the video
Mozilla Developer Network: Numbers
Strings are essentially a number of characters glued together. Strings can form words, sentences, URL's; basically anything. One important aspect of strings is that they are arrays, and like arrays they index at zero. Quotes ("") denote strings. The objective is to manipulate strings into doing what you want, by writing a little program.
Read the article
Copy and paste the article (or any other text) into one long string in your text editor
Change all characters to lower case
Make another string, this time of your name
Using a number of for loops and if statements, capitalise letters in the long text so that it shows your name over and over again
If you get confused, take a look at the Arrays task first
Quirks Mode: Strings
Arrays are lists of data. Some only contain numbers, some contain characters. While strings are arrays, arrays may contain multiple strings. Arrays may even contain multiple arrays! The  brackets are used to indicate arrays.
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Make an array containing the titles of five of your favorite books, movies, series or albums/songs
Add a title once using the push method, once using the unshift method, and once using a different method
Remove a title three times using different methods each time
Mozilla Developer Network: Arrays
Read the articles
Make an object containing the titles of five of your favorite books, movies, series or albums/songs using the creators as keys and the titles as values
Expand the object by making objects within the object for every key, adding subkeys and values for creator, title, year, and the reason why you think this particular artwork is so awesome