Arrays are important!
The first non-primitive data type #
undefined. Other languages have more or fewer. Java and C, for example, differentiate between integers and floating point numbers and deal in individual characters instead of strings. Every language, though, eventually has to deal with more than one piece of information, and the simplest collection of data is the array.
An array is a group of data in sequence. It holds each piece of data (each "element") in order and can hold zero or more elements. The elements of an array can be any type of data, including any of the primitive types, arrays, or objects (which are tricky beasts and will be covered at a later date.) We can read any element by its position in the order (its "index"), we can add, alter, or remove elements at any point. We can even change the order of the elements, if we're careful.
Let's look at a few examples of arrays #
Arrays are usually denoted by enclosing a comma-separated list of values in square brackets.
The simplest array is the empty array.
let arr = ;
Yes, an array can consist of no elements! It's not a terribly useful array, but it still counts. But let's look at two more examples:
let a = [0, 2, 5, 1, 15, 3];
let b = [0, 1, 2, 3, 5, 15];
Each of these arrays consists of six numbers, the same six numbers in this case. But an array can hold more than numbers.
let names = ["Pete", "Tom", "Jane", "Dwane", "Melanie"];
let jumble = [
"rutabaga", 12, false, , null, "12", 12, ["a", 12], undefined, [true],
This type of array might not be terribly useful, but it demonstrates a few interesting traits:
- arrays can have any type as elements, even other arrays
- an array can contain identical pieces of data in multiple positions
- an array can contain empty positions