Datatypes 2

What is a Datatype?

When we are programming we must know what kind of data we are working with. Is our variable a Number, a String, an Object, something else? The programming word for kind of data is datatype. In Javascript there are 3 categories of datatype: simple, collection, and function.

What are the Simple Datatypes?

Data is said to be of a simple type when it can only represent one thing at a time. The simple data types are:

Number

Number Documentation

A Number in javascript can be any number between 9,007,199,254,740,992 and -9,007,199,254,740,992. That's a lot of numbers! Numbers can also include a decimal part. To write a number we just type it out though we cannot use commas!

// some valid numbers
0;
12;
193874;
-100;
234.2304980;
-2345823059830193.13981798;

// some invalid numbers
//┌ Can't use commas!
10,000;
//      ┌ Too many decimal points!
134.1309.7;

String

String Documentation

A String in Javascript can be any string of characters. It is called a string because javascript doesn't see words or meaning, it only sees a bunch of individual characters coming one after the other. There is no maximum length of a string though it is limited by the size of your computer's memory. To write a string we first start with a quote character, then we can have any character except that same quote character then we must end with the same quote character. There are 2 quote characters that Javascript lets you use: single quote -> ' and double quote -> ". All characters inside a string are significant this is including spaces, punctuation, and symbols. Remember: All characters in a string are significant.

// Some valid strings
// ┌ Double Quote               ┌ Double Quote
   "If you can't stand the heat,";
// ┌ Single Quote     ┌ Single Quote
   'stay out of Miami.';
// ┌ The smallest string: empty string!!
   "";
// ┌ This string is 5 space characters
   "     ";
// ┌ Single Quote      ┌ Single Quote
// ⇣           ┌ We can⇣put one quote type inside another
   'We built a "lazer".'

// Some invalid strings
// ┌ Double Quote       ┌ No closing quote!!
   "I thought I told you;
// ┌ Double Quote    ┌ Non matching closing quote!! 
   "That we wont stop'
// ┌ Double Quote                          ┌ Oops!!
   "To take the wold hostage we've built a "Lazer"";

TODO: Escape Sequences

Boolean

Boolean Documentation

A Boolean in programming is a piece of data that can either be true or false and nothing else. There are no other possible values for a Boolean! This is extremely useful as many programming instructions function simply by checking whether a comparison is either true or false. Such simplicity!

// Some valid Booleans
true;
false;
// Thats it!!! Nothing else is a valid Boolean.

// Some invalid booleans.
// This is a string, not a Boolean!!
"true";
// This is not valid, all letters must be lowercase!!
True;

Undefined

Undefined Documentation

In Javascript undefined means no value. When we declare a variable but don't assign it it is undefined. When we write a function that has no return value the function returns undefined.

//   ┌ We declare a variable but don't assign it.
var someVariable;
someVariable === undefined; // This is true

//        ┌ This function doesn't return anything.
function yay(){ 2 + 2; }
yay() === undefined; // This is also true

//   ┌ We declare a person variable and assign it an empty object.
var person = {};
person.name === undefined; // Also true

Coming soon:

• NaN
• Regular Expressions
• Null

What are the Collection Datatypes?

Coming Soon!

What is the Function Datatype?

Coming Soon!