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

npm install have
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Have your arguments, and validate it too:

var have = require('have');

function safeFunc(id, options, callback) {
    { 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
  • 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!


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(cond, message) {
  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(id, options, callback) {
  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)


v0.2.1 - v0.2.2

  • 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.

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