@delucis/aproba

@delucis/aproba
===============

A ridiculously light-weight function argument validator

> _N.B. This is a fork of @iarna’s [aproba][0678a2d4] that adds support for the following ES2015 types: Map, WeakMap, Set, WeakSet, and Symbol. If you don’t need those, [use the original][0678a2d4]!_

[0678a2d4]: https://github.com/iarna/aproba "aproba on GitHub"

``
var validate = require("aproba")

function myfunc(a, b, c) {
// a must be a string, b a number, c a function
validate('SNF', arguments) // [a,b,c] is also valid
}

myfunc('test', 23, function () {}) // ok
myfunc(123, 23, function () {}) // type error
myfunc('test', 23) // missing arg error
myfunc('test', 23, function () {}, true) // too many args error

`

Valid types are:

| type | description
| :--: | :----------
| * | matches any type
| A | Array.isArray OR an arguments object
| S | typeof == string
| N | typeof == number
| F | typeof == function
| O | typeof == object and not types A, E, M, m, C, or c
| B | typeof == boolean
| E | instanceof Error OR null (special: see below)
| Z | == null
| M | instanceof Map
| m | instanceof WeakMap
| C | instanceof Set
| c | instanceof WeakSet
| Y | typeof == symbol

Validation failures throw one of three exception types, distinguished by a
code property of EMISSINGARG, EINVALIDTYPE or ETOOMANYARGS.

If you pass in an invalid type then it will throw with a code of
EUNKNOWNTYPE.

If an error argument is found and is not null then the remaining
arguments are optional. That is, if you say ESO then that's like using a
non-magical E in: E|ESO|ZSO.

$3

You can provide more than one signature by separating them with pipes |.
If any signature matches the arguments then they'll be considered valid.

So for example, say you wanted to write a signature for
fs.createWriteStream. The docs for it describe it thusly:

`
fs.createWriteStream(path[, options])
`

This would be a signature of SO|S. That is, a string and and object, or
just a string.

Now, if you read the full fs docs, you'll see that actually path can ALSO
be a buffer. And options can be a string, that is:
`
path |
options |