norma

A function argument organizer

norma

Sometimes you want your functions to accept optional arguments. It makes your API nicer.

If you're using this module, feel free to contact me on twitter if you have any questions! :) @rjrodger

Current Version: 0.3.0

Tested on: node 0.10.26

Annotated Source

Usage

Let's take an example. Say your the basic function signature is:

myAPI.doStuff( 'the-stuff', function( err, result ){ ... } )

But you also want to support options:

myAPI.doStuff( 'the-stuff', 
               { option1:'foo', option2:'bar'}, 
               function( err, result ){ ... } )

The callback should be the last argument. That's the style. So you have to write a bit of logic to test if the second argument is an object or a function and act appropriately. Ths is cruft code getting in the way of real work.

myAPI.doStuff = function(){
  var stuff    = arguments[0]
  var options  = 'function' == typeof(arguments[1]) ? {} : arguments[1]
  var callback = 'function' == typeof(arguments[2]) ? arguments[2] : arguments[1]
  ...
}

With this module, you specify what you want using a simple expression language:

myAPI.doStuff = function(){
  var args = norma('so?f',arguments)
 
  var stuff    = args[0]
  var options  = args[1] || {}
  var callback = args[2]
}

Now your arguments always come back in a well-defined array, and always at the same index.

The expression 'so?f' means match: a string, an optional object, and a function

You can also assign names:

myAPI.doStuff = function(){
  var args = norma('stuff:s options:o? callback:f',arguments)
  // args == {stuff:..., options:..., callback:...}
  args.options = args.options || {}
}

And of course, if your function is called with arguments that do not match the expression, then an error is thrown.

If you're using this module, feel free to contact me on twitter if you have any questions! :) @rjrodger

Current Version: 0.2.6

Tested on: node 0.10.26

var norma = require('norma')
 
function foo() {
  var args = norma('sf', arguments)
 
  var content = args[0]  // s => string, required
  var cb      = args[1]  // f => function, required
 
  cb(null,content+'!')
}
 
foo('bar',function(err,out){
  console.log(out)
})
npm install norma

Function Signature Expression

The expression you use to define the function argument types that you expect is a string containing individual characters that stand for JavaScript types. Each type is a single character. These are:

  • s - string
  • i - integer
  • n - number
  • b - boolean
  • f - function
  • a - array
  • o - object
  • r - regexp
  • d - date
  • g - arguments
  • e - error
  • N - null
  • U - undefined
  • A - NaN
  • Y - Infinity

You list the types you expect, in the order you expect. The norma module will return an array with each position corresponding to the position of each type letter.

This works like so:

  • "s" => [string] => [ "Foo" ]
  • "si" => [string, integer] => [ "Foo", 123 ]
  • "sbi" => [string, boolean, integer] => [ "Foo", true, 123 ]

The syntax of the expression is similar to a regular expression (but it's not one!). You can use these special characters:

  • . - match any type
  • ? - preceding type is optional (also matches null, undefined, and NaN)
      • preceding type can occur any number of times (including zero)
      • preceding type can occur any number of times (but must occur at least once)
  • | - set of alternate types that are valid in this argument position

Now you can do this:

  • "so?f" => [ string, optional object, function ] => [ "a", function(){...} ]; [ "a", {b:1}, function(){...} ]
  • "s?n" => [ optional string, number ] => [ "a", 1 ]; [ 1 ]
  • "si*" => [ string, zero or more integers... ] => [ "a" ]; [ "a", 1 ]; [ a, 1, 2 ]; [ a, 1, 2, 3 ]
  • "si+" => [ string, one or more integers... ] => [ "a", 1 ]; [ a, 1, 2 ]; [ a, 1, 2, 3 ]
  • "s.*" => [ string, anything... ] => [ "a", true ]; [ a, {}, [] ]; [ a, 3, {}, true, /hola/ ]
  • "s|if" => [ string or integer, function ] => [ "a", function(){...} ]; [ 1, function(){...} ];

You can use whitespace and commas to make things more readable:

  • "so?f" === "s o? f" === "s, o?, f"

If no match is found for a given position, undefined is used as the placeholder:

  • "si*" on [ "a" ] gives [ "a", undefined ]
  • "s.*b" on [ "a", true ] gives [ "a", undefined, true ]

Alternates can also be optional, so this works too:

  • "s|i? b" => [ optional string or integer, boolean ] => [ true ]; [ "a", true ]; [ 1, true ];

Note that you'll get an undefined as the placeholder, as usual:

  • "s|i? b" on [ true ]; [ "a", true ]; [ 1, true ]; gives [ undefined, true ]; [ "a", true ]; [ 1, true ];

You can also give arguments names. These are set as properties on the returned array, as well being assigned an index:

  • "foo:s" => [ "val", foo:"val" ] // in util.inspect output format

If you really want an object, use the form:

  • "{foo:s}" => { foo:"val" }

If you use the * modifier, and a name, then you'll get back an array listing all the matches (zero or more).

  • "{foo:s*}" => { foo: ["v1","v2",...] }

And that's it!

You can compile a pattern ahead of time:

var norma = require('norma')
 
var needstring = norma.compile('s')
 
function foo() {
  var args = needstring( arguments )
  console.log( 'string:'+args[0] ) 
}

The parser uses PEG.js to understand the signature expression, and then it builds an internal regular expression to match the function argument types.

The source code is annotated.

Development

Edit norma-parser.pegjs to modify the grammar. Rebuild with npm run build.

Test with:

npm test