This module provides a simple and standard way of checking for object attributes. The inspiration for this project was checking for the existence of environment variables.

Installation: npm install musthave

This module contains minimal dependencies and helps keep npm fit.

If your application requires the presence of a couple of envrionment variables, it's a good idea to make sure they exist as a simple sanity check when your application launches. The following code will log a warning to the console and throw an error if IMPORTANT_VAR_1 and IMPORTANT_VAR_2 aren't in the environment variables.

var MustHave = require('musthave');
var mh = new MustHave();

mh.hasAll(process.env, 'IMPORTANT_VAR_1', 'IMPORTANT_VAR_2'); // returns boolean

If the hasAll method fails, the missing attributes are available in mh.missing (returned as an array of strings).

If you need to make sure an object has at least one attribute of a specific name, use the hasAny() method.

var MustHave = require('musthave');
var mh = new MustHave();

mh.hasAny(process.env, 'IMPORTANT_VAR_1', 'IMPORTANT_VAR_2'); // returns boolean

The code above will throw an error only if process.env does NOT have IMPORTANT_VAR_1 or IMPORTANT_VAR_2.

If you need to make sure an object has only a specific set of named attributes, use the hasExactly() method.

var MustHave = require('musthave');
var mh = new MustHave();

mh.hasExactly(process.env, 'IMPORTANT_VAR_1', 'IMPORTANT_VAR_2'); // returns boolean

The code above will not throw an error only if process.env has IMPORTANT_VAR_1 and IMPORTANT_VAR_2. If process.env has both of these and another attribute like NODE_ENV, this method will throw an error because the object is not exactly as defined. You probably don't want to use this on process.env because it can change from system to system, but it can be useful on other kinds of objects like data models.

If you want to suppress warning messages, the MustHave module can be configured to do so. It can also be configured to not throw errors so your app can handle them as it sees fit. To accomodate these use cases, there are two configuration options that can be passed to the MustHave() object. Not providing a configuration is the same as:

var MustHave = require('musthave');
var mh = new MustHave({
  throwOnError: true,      // Set this to false if you want to handle errors on our own
  suppressWarnings: false  // Set this to true if you don't want console output for warnings.
});