Type insurance

Helper class to force (input) types, mainly for pure JavaScript environments

Key notes / highlights

• Multi type container
• Ensures a type for a variable declaration (in opposition to type checking)
• e.g. when using the type 'any'
• Tailored for non type sensitive environments
• Useful when working with uncertain data from third party API's
• Returns actually false for empty objects (or any other implicitely falsy value)
• Simplistic approach
• Doesn't extend the built in .prototypes
• Clean and focused

Install

$ npm install type-insurance

Usage (real world example)

import TypeInsurance from 'type-insurance';

export const stripHTML = input => {
    const { string } = new TypeInsurance(input);
    return string.replace(/<[^>]*>/g, '');
}

This little utility function sanitizes an input parameter from HTML tags. TypeInsurance is used to force the regex to obtain a string no matter what.

Usage (overview)

import TypeInsurance from 'type-insurance';
// or using CommonJS
//const TypeInsurance = require('type-insurance');

const input = new TypeInsurance('foo');

console.log(input.string);  // "foo" 
console.log(input.number);  // 440071440
console.log(input.boolean); // true
console.log(input.array);   // ["foo"]
console.log(input.object);  // { key: "foo" }

const arr = new TypeInsurance([1, 2, 3]);

console.log(arr.string);  // "[1, 2, 3]" 
console.log(arr.number);  // 6
console.log(arr.boolean); // true
console.log(arr.array);   // [1, 2, 3]
console.log(arr.object);  // { 0: 1, 1: 2, 3: 2 }

// ...

Assumptions

"Object", hereinafter is understood as a "real" object, meaning the the intersection of the sets "objects" and "not arrays".

All inputs should return themselves when requesting its original type. And all falsy values except false should map to

• '' (string)
• 0 (number)
• false (boolean)
• [] (array)
• {} (object)

The inputs [] and {} should be treated as falsy inputs.

A non-empty string should map to

• The decimal representation of a hash conversion, unless the string contains only digits (number)
• true (bool)
• An array containing the string (array)
• An object with the default key and the string as the value (object)

where the edge case 'false' should return false when requesting the .boolean property. Numbers shall work in an analogous fashion. 0 especially should yield false.

Respectively, true|false should return '1'|'0', 1|0 and [true|false].

API

Constructor: new TypeInsurance(input, [options])

A class instance of TypeInsurnace holds the properties .string, .number, .boolean, .array and .object, each in turn holding the accordingly typed values mapped from the input value.

Options get passed in as an object. Available options are:

• defaultKey (default: "key") - Specifies the default key for implicitly generated objects from strings and numbers
• hashObjects (default: false) - The .number prop returns a hash for object inputs
• stringifyBoolsVerbatim (default: false) - The .string prop returns stringified versions ('true'|'false') for boolean inputs

Properties

.string

Returns a string generated from the input of the constructor.

Input type	Output
string	unchanged input
number	Series of stringified digits
boolean	'1' / '0'
array	Stringified version of the array content
object	Stringified version of the object content

.number

Returns a number generated from the input of the constructor.

Input type	Output
string	Hash converted to decimal
number	unchanged input
boolean	1 / 0
array	Sum of all elemets
object	Sum of all object values

.boolean

Returns a number generated from the input of the constructor.

Input type	Output
string	true if input is non-empty
number	false if input === 0
boolean	unchanged input
array	false if input === []
object	false if input === {}

.array

Returns an array generated from the input of the constructor.

Input type	Output
string	Array containing input
number	see above line
boolean	see above line
array	unchanged input
object	Object.values(input)

.object

Returns an array generated from the input of the constructor.

Input type	Output
string	Object containing the key value pair [defaultKey]=input
number	see above line
boolean	see above line
array	{...input}
object	unchanged input

Keywords

• data
• interface
• type
• types
• convert
• safety

Dependencies

• hash-sum
• has-own-prop
• lodash

Related

• typeablejs - A library for checking and casting types.
• @sindresorhus/is - Type check values

Maintainer

• Ruben Giannotti - ruben.giannotti@gmx.net - github.com/giannotr