How to read the reference documentation

Please take a moment to familiarize yourself with the types of symbols you'll see throughout the technical documentation.

Type Annotations

This shorthand is used to indicate the types of arguments, return values, and object properties.

Annotation
Meaning
\[day]
The parameter is optional. If it is not supplied, it will be undefined.
\[day="Monday"]
The parameter is optional, but will be supplied a default value if not provided.
?Array
Type can be an Array OR null.
!Array
Type must be an Array; cannot be null. Primitive types (string, number, boolean) imply ! unless explicitly denoted otherwise with ?.
string | number
Type can be either string or number.
{foo:number, bar:string}
Type is an object with two properties: foo, which is type number; and bar, which is type string.
string\[]
Type is an array of strings.
Array<string>
Type is an array of strings.
Promise<string>
Type is a Promise that is asynchronously fulfilled with a string.
*
Can be any type. NOTE: In this early stage, * is sometimes used as a placeholder for incomplete documentation.