Variables are containers for data,and like many other containers they are often labelled with a name. Because confusing H2O with H2O2 by mistake will most likely kill you, it is useful to label your containers so that you have a good idea what is inside. In this case "water" and "hydrogen peroxide" would be apt container names. Sensible variable names makes code more readable and is considered good programming practice.
Javascript is a so called "dynamically typed language", which means variables only have to be declared as variables and not as the type of variable it is. In other words, a programmer only has to say "this is a variable", and Javascript does the rest of the work. This is in stark contrast with languages such as C, in which you not only have to say that something is a number, but also what kind of number. Since Javascript has only three types of data, this problem is not encountered often.
Watch the video
Read the article
Youtube - The New Boston: Different Types of Variables
Tutorials Point: Javascript Variables
Scope is the concept of where variables can be accessed. For example, a variable that is declared within a function cannot really be accessed from the outside. However, a variable outside a function can be accessed from within the function. Scope is very important to keep in mind, because faulty scoping can mess up any program.
Watch the video
Read the article
Write a short program as an example of how to use scope
Include at least one local and one global variable
Use comments to provide deeper explanation
Explain the concept of scope to a friend, parent or your landlord using the example you just wrote
Hand in the example by posting a gist link on Slack
Javascript Workflow for Dummies: Scopes and Variables
Youtube - The New Boston: Global & Local Variables
In the new Javascript there are two different types of variables. Var is the one mostly used, let is the new one. Chances are you will seldom or never use the latter. Let is a special type of variable that can only be accessed in the code block where it is declared in. Keep in mind that this is such a new technology, you do not really have to master it. However, it lets you get a closer look at the principle of scope and a slight glipse into the future of Javascript.
Read the article
Mozilla Developer Network: Let