assert-options

What is assert-options?

The assert-options npm package is a utility for validating and asserting options in JavaScript objects. It helps ensure that the options passed to a function or module are valid and meet the expected criteria.

What are assert-options's main functionalities?

Basic Option Validation

This feature allows you to validate and merge user-provided options with default options. If the user does not provide an option, the default value is used.

const assertOptions = require('assert-options');

function myFunction(options) {
  const defaultOptions = { a: 1, b: 2 };
  options = assertOptions(options, defaultOptions);
  console.log(options);
}

myFunction({ a: 10 }); // { a: 10, b: 2 }
myFunction(); // { a: 1, b: 2 }

Strict Option Validation

This feature enforces strict validation, ensuring that only the specified options are allowed. If an unknown option is provided, an error is thrown.

const assertOptions = require('assert-options');

function myFunction(options) {
  const defaultOptions = { a: 1, b: 2 };
  options = assertOptions(options, defaultOptions, { strict: true });
  console.log(options);
}

myFunction({ a: 10, c: 3 }); // Throws an error because 'c' is not a valid option

Nested Option Validation

This feature supports validation of nested options, allowing you to merge and validate deeply nested objects.

const assertOptions = require('assert-options');

function myFunction(options) {
  const defaultOptions = { a: 1, b: { c: 2, d: 3 } };
  options = assertOptions(options, defaultOptions);
  console.log(options);
}

myFunction({ b: { c: 10 } }); // { a: 1, b: { c: 10, d: 3 } }
myFunction(); // { a: 1, b: { c: 2, d: 3 } }

Other packages similar to assert-options

joi

Joi is a powerful schema description language and data validator for JavaScript. It allows you to create blueprints or schemas for JavaScript objects to ensure validation. Compared to assert-options, Joi offers more advanced and flexible validation capabilities, including support for complex data types and custom validation rules.

yup

Yup is a JavaScript schema builder for value parsing and validation. It is similar to Joi but is often preferred for its simplicity and ease of use. Like assert-options, Yup can validate and transform objects, but it provides more comprehensive validation features and better integration with form libraries.

prop-types

Prop-types is a runtime type checking library for React props. While it is primarily used for validating React component props, it can also be used for general object validation. Compared to assert-options, prop-types is more focused on type checking rather than option validation and merging.

README

assert-options

Smart options-object handling, with one line of code:

• throw detailed error on invalid options
• set default values for missing options

Strongly-typed, built with TypeScript 4.x strict mode, for JavaScript clients.

Rationale

• Passing in invalid or misspelled option names is one of the most common errors in JavaScript.
• Assigning defaults is the most common operation for methods that take options.

This module automates proper options handling - parsing + setting defaults in one line.

Although this library is implemented in TypeScript, its objective is mainly to help JavaScript clients, because TypeScript itself can handle invalid options and defaults natively.

Installation

$ npm i assert-options

Usage

const { assertOptions } = require('assert-options');

function functionWithOptions(options) {
    options = assertOptions(options, {first: 123, second: null});
    
    // options is a safe object here, with all missing defaults set.
}

When default values are not needed, you can just use an array of strings:

function functionWithOptions(options) {
    options = assertOptions(options, ['first', 'second']);
    
    // the result is exactly the same as using the following:
    // options = assertOptions(options, {first: undefined, second: undefined});
    
    // options is a safe object here, without defaults.
}

You can override how errors are thrown, by creating the assert function yourself, and specifying a custom handler:

const {createAssert} = require('assert-options');

// must implement IOptionsErrorHandler protocol
class MyErrorHanler {
    handle(err, ctx) {
        // throw different errors, based on "err"
        // for reference, see DefaultErrorHandler implementation 
    }
}

const assert = createAssert(new MyErrorHanler());

API

assertOptions(options, defaults)

• When options is null/undefined, new {} is returned, applying defaults as specified.

• When options contains an unknown property, Error Option "name" is not recognized. is thrown.

• When a property in options is missing or undefined, its value is set from the defaults, provided it is available and its value is not undefined.

• When options is not null/undefined, it must be of type object, or else TypeError is thrown: Invalid "options" parameter: value.

• Parameter defaults is required, as a non-null object or an array of strings, or else TypeError is thrown: Invalid "defaults" parameter: value.

createAssert(handler)

Creates a new assert function, using a custom error handler that implements IOptionsErrorHandler protocol.

For example, the default assertOptions is created internally like this:

const {createOptions, DefaultErrorHandler} = require('assert-options');

const assertOptions = createAssert(new DefaultErrorHandler());