Variables

What is a Variable?

A variable is just a name for some data.
That's it?!? Yep!

How do we make them?

Making variables is called declaration and it looks like this:

// ┌ First we need var
// ⇣   ┌ Then a name
  var sheena;

But, that doesn't have any data, just a name! Correct! Let's give sheena some data. This is called assignment and to do it we use the assignment operator. The assignment operator to non-programmers is called the equals sign and we use it to assign a variable to some data like so:

  var sheena;
// ┌ 1st comes our variable name on the left
// ⇣     ┌ Then the assignment operator
  sheena = "a punk rocker";
//           └ Then some data 

It is very common to combine these two steps into one like so:

// Try to answer, 
// what are the 4 parts of this variable declaration and assignment called?
// 1   2     3   4
// ⇣   ⇣     ⇣   ⇣   
  var sheena = "a punk rocker";

How do I change what a variable is assigned to?

This is called reassignment and we again use the assignment operator:

//  Here we declare a variable and assign it to some data
var clarkKent = "a mild mannered news reporter";

// After a cry for help we reassign the variable
clarkKent = "the man of steel";

What kind of data can a variable be assigned to?

In Javascript a variable can be assigned to any kind of data!! In programming a kind of data is referred to as a Datatype.

var theEarthIsRound = true;
var elephantsDont = ["swim", "drive", "wear pants"];
var myFavoriteAnimal = "jackalope";
var clownsThatCanFitInASinglePhoneBooth = 64;
// and so on

What kind of things can I name my variable?

Here are some rules:

• A variable name must be at least 1 character long.
• The first character must be a letter -or- _ -or- $.
• Any characters after that can also be numbers
• A variable name cannot contain any spaces!

Here are some guidelines:

• start your variable with a lowercase letter
• use Camel Case
• use descriptive but short names

Some examples:

var x = "marks the spot";
var batman2 = "the dark knight";
var numberOfStudents = 9;
var ___z___$504___ = "i'm a rediculous variable name";

For those that want a visual description of valid variable names:

IMPORTANT!

Variable names are case sensitive! That means that lower case letters and uppercase letters are not interchangeable! For example:

// These two variables are not the same!
//  ┌ This one starts with a lower case letter
var halleBotStatus;
//  ┌ This one starts with an upper case letter
var HalleBotStatus;

How do I use variables?

You just use their name! Since variables are assigned to data, when we use their names it's just like we're typing out all the data.

// Here we create a variable an assign it to some text
var drEvilLifeStory = "My father was a relentlessly self-improving boulangerie owner from Belgium with low grade narcolepsy and a penchant for buggery. My childhood was typical, summers in Rangoon, luge lessons. In the spring we'd make meat helmets.";
// Now we don't have to type that text anymore, 
// we can just use the variable by name!

// Here we are using the text multiple times by just using the variable
tellUsAboutYourself( drEvilLifeStory );
imSorryIDidntHearYou( drEvilLifeStory );
couldYouRepeatThat( drEvilLifeStory );
itsTooLoudInHereLetsGoOutsideWhereICanHearYou( drEvilLifeStory );

What else can variables do?

Nothing!! Variables are just names for data! 👍