Have your arguments, and validate it too. -- Slick arguments validator for all your js functions.


Have your arguments, and validate it too:

var have = require('have');
function safeFunc(idoptionscallback) {
    { id       : 'string or number'
    , options  : 'optional object'
    , callback : 'function'

HAVE.js gives you a mini-DSL to quickly validate your function arguments.


In order of precedence:

  • opt X|optional X - Optional X
  • X or Y - Either X or Y
  • X a|X arr|x array - Array of X
  • s|str|string - String
  • n|num|number - Number
  • b|bool|boolean - Boolean
  • f|fun|func|function - Function
  • a|arr|array - Array
  • o|obj|object - Object
  • r|rx|regex|regexp - RegExp
  • d|date - Date

These matchers can be combined. These are all valid HAVE.js matchers:

  • str or num array - String or Array of Number
  • num arr or str arr - Array of Number or Array of String
  • num a a a a - Array of Array of Array of Array of Number
  • opt str or num array - Optional (String or Array of Number)

Have fun!


The HAVE.js function also returns any parsed argument collected in a hash keyed to the same key as was given in the schema. You can inspect the returned object to more easily obtain the parsed value without having to duplicate the HAVE.js parsing logic in your code to extract them.

See @wmakeev PR for an example.


If you are like me and you write a lot of method preconditions that should be turned off or atleast, should not throws in production, you can replace HAVE.js assert function like so:

var have = require('have');
have.assert(function(condmessage) {
  if (!cond) {
    console.log('WARN: assertion failed: ' + message);

This will replace the assert function HAVE.js uses internally with your implementation so if you want to completely turns assertion off, then just give it a no-op function.


For those who like it short, the above example can also be written like this:

var have = require('have');
function safeFunc(idoptionscallback) {
  have(arguments, { id: 's or n', options: 'opt o', callback: 'f' });

This is not very readable, of course. But HAVE.js does not dictate your readability preference for you. So go wild if you think it is ok : )


BSD (if you don't like BSD, just contact me)


  • (credit: @wmakeev) The function now returns parsed arguments as a hash object.
  • Adds the forgotten boolean support.
  • Eat null and undefined where optional argument is expected.


Test with npm test or make test.

Just open a new GitHub issue or ping me @chakrit on Twitter.

Pull requests and feature suggestions totally welcome.