istypes

istypes is a library that allows type-checking of javascript instances and also a way to group a list of items by type.

Installation

$ npm install --save istypes

or

$ yarn add istypes

Usage

Type checking API:

All samples are included in tests to guarantee their validity

import { check } from 'istypes';

// positives
check.isUndefined(undefined) // true
check.isNull(null) // true
check.isBoolean(true)  // true
check.isNumber(0)  // true
check.isNumber(parseInt('x')) // true (NaN is a number)
check.isNumber(1 / 0)  // true (+Infinity is a number)
check.isString('') // true
check.isArray([])  // true
check.isObject({}) // true
check.isFunction(() => {}) // true
(function () {
    check.isArguments(arguments) // true
})()
check.isRegExp(/.*/)     // true
check.isDate(new Date()) // true

// negatives
check.isNotUndefined(undefined) // false
check.isNotNull(null) // false
check.isNotBoolean(true)  // false
check.isNotNumber(0)  // false
check.isNotNumber(parseInt('x')) // false (NaN is a number)
check.isNotNumber(1 / 0)  // false (+Infinity is a number)
check.isNotString('') // false
check.isNotArray([])  // false
check.isNotObject({}) // false
check.isNotFunction(() => {}) // false
(function () {
    check.isNotArguments(arguments) // false
})()
check.isNotRegExp(/.*/)     // false
check.isNotDate(new Date()) // false

Checks for primitives:

isPrimitive(test)

A test for primitive-ness as found on stackoverflow:

console.log([
  // promitives :
  undefined,
  null,
  true,
  false,
  0,
  parseInt('x'),
  1 / 0,
  -1 / 0,
  '',
  Symbol.iterator,

  // complex:
  [],
  {},
  function () {
  },
  arguments,
  /$/,
  new Date(),
  new Error('')
].map(check.isPrimitive));

Outputs:

[ true, // undefined,
  true, // null,
  true, // true,
  true, // false,
  true, // 0,
  true, // parseInt('x'),
  true, // 1 / 0,
  true, // -1 / 0,
  true, // '',
  true, // Symbol.iterator,
  false,
  false,
  false,
  false,
  false,
  false,
  false ]

isNotPrimitive(test)

Returns exactly opposite of isPrimitive(test)

Checks for iterables:

TODO: add explanation

isIterable(test) and isNotIterable(test)

TODO: add sample code

Checks for array-like objects:

TODO: add explanation

isArrayLike(test) and isNotArrayLike(test)

TODO: add sample code

Type extraction

console.log([
    undefined,
    null,
    false,
    0,
    '',
    [],
    {},
    function () {
    },
    arguments,
    /$/,
    new Date()
].map(check.getType))

Outputs:

[ 'undefined',
  'null',
  'boolean',
  'number',
  'string',
  'array',
  'object',
  'function',
  'arguments',
  'regexp',
  'date' ]

Extensibility

Checks are available even for types not included in the library:

import { check as checkGen } from 'istypes';

const check = checkGen(new Map(), new Set(), new Error(), Symbol.iterator, Buffer.from(''));

check.isUndefined(undefined) // true
check.isMap(new Map()) // true
check.getType(new Set()) // 'set'
check.isError(new Error()) // true
check.isSymbol(Symbol.species) // true
// here is a small catch with Buffer:
check.isUint8Array(Buffer.from('123')) // true, after all, Buffer is a type 'Uint8Array'
check.getType(Buffer.from('456')) // 'uint8array'

Methods getType(input), isPrimitive(test), and isNotPrimitive(test) are not affected by extensibility.

Grouping by type:

A convenience method to stack values of an array-like object (e.g. arguments) under the keys named after items' types in a simple object.

import { groupByType } from 'istypes';

function (/* variable signature, name? : string, options? : object, callback? : function */) {
  const grouped = groupByType(argusments);
  
  if (grouped.string) {
    // name provided
  }
  
  if (grouped.object) {
    // options provided
  }
  
  if (grouped['function']) {
    // callback provided
  }
  
  // ...
}

Contributing

Please use the issues page to report a bug or request a feature.

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License

MIT

Author

Andrew Revinsky