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 castInput = new TypeInsurance(input);
	return castInput.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);   // ["f", "o", "o"]
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 on the first index and its single letters on the consecutive indices (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 the single letters of the input | | number | Array containing the digits of the input number | | boolean | see 'string' | | 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 - [email protected] - github.com/giannotr