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

1$ npm install --save istypes

or

1$ yarn add istypes

Usage

Type checking API:

All samples are included in tests to guarantee their validity

1
2import { check } from 'istypes';
3
4// positives
5check.isUndefined(undefined) // true
6check.isNull(null) // true
7check.isBoolean(true)  // true
8check.isNumber(0)  // true
9check.isNumber(parseInt('x')) // true (NaN is a number)
10check.isNumber(1 / 0)  // true (+Infinity is a number)
11check.isString('') // true
12check.isArray([])  // true
13check.isObject({}) // true
14check.isFunction(() => {}) // true
15(function () {
16    check.isArguments(arguments) // true
17})()
18check.isRegExp(/.*/)     // true
19check.isDate(new Date()) // true
20
21// negatives
22check.isNotUndefined(undefined) // false
23check.isNotNull(null) // false
24check.isNotBoolean(true)  // false
25check.isNotNumber(0)  // false
26check.isNotNumber(parseInt('x')) // false (NaN is a number)
27check.isNotNumber(1 / 0)  // false (+Infinity is a number)
28check.isNotString('') // false
29check.isNotArray([])  // false
30check.isNotObject({}) // false
31check.isNotFunction(() => {}) // false
32(function () {
33    check.isNotArguments(arguments) // false
34})()
35check.isNotRegExp(/.*/)     // false
36check.isNotDate(new Date()) // false
37

Checks for primitives:

isPrimitive(test)

A test for primitive-ness as found on stackoverflow:

1
2console.log([
3  // promitives :
4  undefined,
5  null,
6  true,
7  false,
8  0,
9  parseInt('x'),
10  1 / 0,
11  -1 / 0,
12  '',
13  Symbol.iterator,
14
15  // complex:
16  [],
17  {},
18  function () {
19  },
20  arguments,
21  /$/,
22  new Date(),
23  new Error('')
24].map(check.isPrimitive));
25

Outputs:

1[ true, // undefined,
2  true, // null,
3  true, // true,
4  true, // false,
5  true, // 0,
6  true, // parseInt('x'),
7  true, // 1 / 0,
8  true, // -1 / 0,
9  true, // '',
10  true, // Symbol.iterator,
11  false,
12  false,
13  false,
14  false,
15  false,
16  false,
17  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

1console.log([
2    undefined,
3    null,
4    false,
5    0,
6    '',
7    [],
8    {},
9    function () {
10    },
11    arguments,
12    /$/,
13    new Date()
14].map(check.getType))

Outputs:

1[ 'undefined',
2  'null',
3  'boolean',
4  'number',
5  'string',
6  'array',
7  'object',
8  'function',
9  'arguments',
10  'regexp',
11  'date' ]

Extensibility

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

1
2import { check as checkGen } from 'istypes';
3
4const check = checkGen(new Map(), new Set(), new Error(), Symbol.iterator, Buffer.from(''));
5
6check.isUndefined(undefined) // true
7check.isMap(new Map()) // true
8check.getType(new Set()) // 'set'
9check.isError(new Error()) // true
10check.isSymbol(Symbol.species) // true
11// here is a small catch with Buffer:
12check.isUint8Array(Buffer.from('123')) // true, after all, Buffer is a type 'Uint8Array'
13check.getType(Buffer.from('456')) // 'uint8array'
14

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.

1import { groupByType } from 'istypes';
2
3function (/* variable signature, name? : string, options? : object, callback? : function */) {
4  const grouped = groupByType(argusments);
5  
6  if (grouped.string) {
7    // name provided
8  }
9  
10  if (grouped.object) {
11    // options provided
12  }
13  
14  if (grouped['function']) {
15    // callback provided
16  }
17  
18  // ...
19}
20

Contributing

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

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License

MIT

Author

Andrew Revinsky