Why should I split a string?
Splitting strings can be used for a lot of different purposes. Maybe you want to read a sentence word by word or read a word letter by letter.
The point is that there is a lot of different things you need this for and it's easy to forget the syntax if you don't use it often.
A simple example
var str = "This is a sentence.";
var splitted = str.split(" ");
You should now have an array with four elements (['This', 'is', 'a', 'sentence.']). You can now access one of the values, iterate over them reverse them, etc.
Splitting with a limit
Let's say that we have the same sentence (This is a sentence.) and you want to split it and get the two first words.
var str = "This is a sentence.";
var splitted = str.split(" ", 2);
As you can see, the code is very similar, but we passed in another parameter (2). If you print out the "splitted" array now, you should see two elements: ['This', 'is']
Separators
You can use what ever you want as the separator. It can be a space, a letter, a sign, multiple letters, etc. And you can even leave it blank. If you leave it blank, it will split the string between each character.
Other relevant JavaScript tutorials
How to replace a string
How to check if a string starts with a certain word