Array #

Arrays are defined with square brackets [] and may contain one type of data:

Supported Types #

• Strings
• Numbers
• Bools
• Regexes
• Paths
• Tuples
• Objects
• Other arrays

Examples of valid arrays #

[1, -2, 3_456] // array of numbers, mind the spaces  ✅
['foo', "bar"] // array of strings  ✅
[true, true, false, true] // array of bools  ✅
[@/file.joe, @/another/file.joe] // array of paths  ✅
[/[a-z]/i, /[0-9]/g] // array of regexes  ✅
[<"foo", 3.14, false>, <'bar', 900, true>] // array of tuples of shape <string, number, bool>  ✅
[{a: 4, b: 'c'}] // array of objects of shape {a: number, b: string}  ✅

Assigning to a variable #

When assigning to a variable, if the array has at least one item in it, joelang can infer the underlying type. On the other hand when assigning an empty array, the type must be specified.

// infer type is number[]
const numbers = [1, 2];  ✅

// invalid since there are mixed types
const numbers = [1, '2'];  ❌

// instantiating an empty array
let myArray: bool[] = [];  ✅

Conditional items #

One of the frustrations developers face is conditionally adding an item to an array. joelang has an easy syntax for that:

[1, 2 if condition, 3]

If condition is true, the array with be [1, 2, 3]. If condition is false, the array with be [1, 3]

Nesting arrays #

Nesting arrays of the same type #

Arrays can be nested, provided they are of the same type. In this example chess game, several Piece type arrays can together form a 2-dimensional array.

const chess: Piece[][] = [];

Nesting arrays of different types should use a tuple #

A string[] array and a number[] array cannot be in the same outer array. For that, you can use a tuple

const someOtherGame: <string[], number[], bool[]> = <[1, 2], ['foo', 'bar'], [true, true]>;