dependon

A node.js module for easily enforcing correct arguments

dependon is simply a wrapper of sorts in order to make checking arguments and throwing errors look cleaner. dpendon takes advantage of higher order functions in order to check arguments. The node.js module, functioner is recommended, but you are free to use whichever library you like best.

Installation

$ npm install dependon

Usage

var dependon = require('dependon');
var being = require('functioner').assert;

// without dependon
function sqrt(x) {
  if (typeof x !== 'number') {
    throw new Error('x should be a positive number');
  }
  if (x <= 0) {
    throw new Error('x should be a positive number');
  }

  return Math.sqrt(x);
}

// with dependon and functioner
function sqrt(x) {
  dependon(x, being.type('number'), being.positive,
      'x should be a positive number');

  return Math.sqrt(x);
}

dependon is really just a function that takes a value as its first parameter, as many functions as you want next, and lastly a string for the error message, and optionally an error type after the message.

// using just dependon
dependon(x, function(x) {
  return x > 0;
}, 'x should be greater than 0', RangeError);

functioner makes dependon a lot more powerful with its ability to build functions to call on the value in order to assert it.

// more complex usage of functioner
var f = require('functioner').assert;

dependon(x, f.type('string'), 'x should be a string');
dependon(x,
    f.compose(f.gte(3), f.accessor('length')),
    'x should be at least 3 in length');
dependon(x, f.between(3, 5), 'x should be between 3 and 5', RangeError);