How to read signatures
- Core
- Optional
- Tooling
Signature sections typically look like this:
vnode = m(selector, attributes, children)
Argument | Type | Required | Description |
---|---|---|---|
selector |
String|Object |
Yes | A CSS selector or a component |
attributes |
Object |
No | HTML attributes or element properties |
children |
Array<Vnode>|String|Number|Boolean |
No | Child vnodes. Can be written as splat arguments |
returns | Vnode |
A vnode |
The signature line above the table indicates the general syntax of the method, showing the name of the method, the order of its arguments and a suggested variable name for its return value.
The Argument column in the table indicates which part of the signature is explained by the respective table row. The returns
row displays information about the return value of the method.
The Type column indicates the expected type for the argument.
A pipe (|
) indicates that an argument is valid if it has any of the listed types. For example, String|Object
indicates that selector
can be a string OR an object.
Angled brackets (< >
) after an Array
indicate the expected type for array items. For exampe, Array<String>
indicates that the argument must be an array and that all items in that array must be strings. Angled brackets after an Object
indicate a map. For example, Object<String,Component>
indicates that the argument must be an object, whose keys are strings and values are components
Sometimes non-native types may appear to indicate that a specific object signature is required. For example, Vnode
is an object that has a virtual DOM node structure.
The Required column indicates whether an argument is required or optional. If an argument is optional, you may set it to null
or undefined
, or omit it altogether, such that the next argument appears in its place.
Optional arguments
Function arguments surrounded by square brackets [ ]
are optional. In the example below, url
is an optional argument:
m.request([url,] options)
Splats
A splat argument means that if the argument is an array, you can omit the square brackets and have a variable number of arguments in the method instead.
In the example at the top, this means that m("div", {id: "foo"}, ["a", "b", "c"])
can also be written as m("div", {id: "foo"}, "a", "b", "c")
.
Splats are useful in some compile-to-js languages such as Coffeescript, and also allow helpful shorthands for some common use cases.
Function signatures
Functions are denoted with an arrow (->
). The left side of the arrow indicates the types of the input arguments and the right side indicates the type for the return value.
For example, parseFloat
has the signature String -> Number
, i.e. it takes a string as input and returns a number as output.
Functions with multiple arguments are denoted with parenthesis: (String, Array) -> Number
License: MIT. © Leo Horie.