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# type
## Runtime validation and processing of JavaScript types
- Respects language nature and acknowledges its quirks
- Allows coercion in restricted forms (rejects clearly invalid input, normalizes permissible type deviations)
- No transpilation implied, written to work in all ECMAScript 3+ engines
### Example usage
Bulletproof input arguments normalization and validation:
```javascript
const ensureString = require('type/string/ensure')
, ensureDate = require('type/date/ensure')
, ensureNaturalNumber = require('type/natural-number/ensure')
, isObject = require('type/object/is');
module.exports = (path, options = { min: 0 }) {
path = ensureString(path, { errorMessage: "%v is not a path" });
if (!isObject(options)) options = {};
const min = ensureNaturalNumber(options.min, { default: 0 })
, max = ensureNaturalNumber(options.max, { isOptional: true })
, startTime = ensureDate(options.startTime, { isOptional: true });
// ...logic
};
```
### Installation
```bash
npm install type
```
## Utilities
Serves following kind of utilities:
##### `*/coerce`
Restricted coercion into primitive type. Returns coerced value or `null` if value is not coercible per rules.
##### `*/is`
Object type/kind confirmation, returns either `true` or `false`.
##### `*/ensure`
Value validation. Returns input value (in primitive cases possibly coerced) or if value doesn't meet the constraints throws `TypeError` .
Each `*/ensure` utility, accepts following options (eventually passed with second argument):
- `isOptional` - Makes `null` or `undefined` accepted as valid value. In such case instead of `TypeError` being thrown, `null` is returned.
- `default` - A value to be returned if `null` or `undefined` is passed as an input value.
- `errorMessage` - Custom error message (`%v` can be used as a placeholder for input value)
---
### Value
_Value_, any value that's neither `null` nor `undefined` .
#### `value/is`
Confirms whether passed argument is a _value_
```javascript
const isValue = require("type/value/is");
isValue({}); // true
isValue(null); // false
```
#### `value/ensure`
Ensures if given argument is a _value_. If it's a value it is returned back, if not `TypeError` is thrown
```javascript
const ensureValue = require("type/value/ensure");
const obj = {};
ensureValue(obj); // obj
ensureValue(null); // Thrown TypeError: Cannot use null
```
---
### Object
_Object_, any non-primitive value
#### `object/is`
Confirms if passed value is an object
```javascript
const isObject = require("type/object/is");
isObject({}); // true
isObject(true); // false
isObject(null); // false
```
#### `object/ensure`
If given argument is an object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureObject = require("type/object/ensure");
const obj = {};
ensureObject(obj); // obj
ensureString(null); // Thrown TypeError: null is not an object
```
---
### String
_string_ primitive
#### `string/coerce`
Restricted string coercion. Returns string presentation for every value that follows below constraints
- is implicitly coercible to string
- is neither`null` nor `undefined`
- its `toString` method is not `Object.prototype.toString`
For all other values `null` is returned
```javascript
const coerceToString = require("type/string/coerce");
coerceToString(12); // "12"
coerceToString(undefined); // null
```
#### `string/ensure`
If given argument is a string coercible value (via [`string/coerce`](#stringcoerce)) returns result string.
Otherwise `TypeError` is thrown.
```javascript
const ensureString = require("type/string/ensure");
ensureString(12); // "12"
ensureString(null); // Thrown TypeError: null is not a string
```
---
### Number
_number_ primitive
#### `number/coerce`
Restricted number coercion. Returns number presentation for every value that follows below constraints
- is implicitly coercible to number
- is neither `null` nor `undefined`
- is not `NaN` and doesn't coerce to `NaN`
For all other values `null` is returned
```javascript
const coerceToNumber = require("type/number/coerce");
coerceToNumber("12"); // 12
coerceToNumber({}); // null
coerceToNumber(null); // null
```
#### `number/ensure`
If given argument is a number coercible value (via [`number/coerce`](#numbercoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureNumber = require("type/number/ensure");
ensureNumber(12); // "12"
ensureNumber(null); // Thrown TypeError: null is not a number
```
---
#### Finite Number
Finite _number_ primitive
##### `finite/coerce`
Follows [`number/coerce`](#numbercoerce) additionally rejecting `Infinity` and `-Infinity` values (`null` is returned if given values coerces to them)
```javascript
const coerceToFinite = require("type/finite/coerce");
coerceToFinite("12"); // 12
coerceToFinite(Infinity); // null
coerceToFinite(null); // null
```
##### `finite/ensure`
If given argument is a finite number coercible value (via [`finite/coerce`](#finitecoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureFinite = require("type/finite/ensure");
ensureFinite(12); // "12"
ensureFinite(null); // Thrown TypeError: null is not a finite number
```
---
#### Integer Number
Integer _number_ primitive
##### `integer/coerce`
Follows [`finite/coerce`](#finitecoerce) additionally stripping decimal part from the number
```javascript
const coerceToInteger = require("type/integer/coerce");
coerceToInteger("12.95"); // 12
coerceToInteger(Infinity); // null
coerceToInteger(null); // null
```
##### `integer/ensure`
If given argument is an integer coercible value (via [`integer/coerce`](#integercoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureInteger = require("type/integer/ensure");
ensureInteger(12.93); // "12"
ensureInteger(null); // Thrown TypeError: null is not an integer
```
---
#### Safe Integer Number
Safe integer _number_ primitive
##### `safe-integer/coerce`
Follows [`integer/coerce`](#integercoerce) but returns `null` in place of values which are beyond `Number.MIN_SAFE_INTEGER` and `Number.MAX_SAFE_INTEGER` range.
```javascript
const coerceToSafeInteger = require("type/safe-integer/coerce");
coerceToInteger("12.95"); // 12
coerceToInteger(9007199254740992); // null
coerceToInteger(null); // null
```
##### `safe-integer/ensure`
If given argument is a safe integer coercible value (via [`safe-integer/coerce`](#safe-integercoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureSafeInteger = require("type/safe-integer/ensure");
ensureSafeInteger(12.93); // "12"
ensureSafeInteger(9007199254740992); // Thrown TypeError: null is not a safe integer
```
---
#### Natural Number
Natural _number_ primitive
##### `natural-number/coerce`
Follows [`integer/coerce`](#integercoerce) but returns `null` for values below `0`
```javascript
const coerceToNaturalNumber = require("type/natural-number/coerce");
coerceToNaturalNumber("12.95"); // 12
coerceToNaturalNumber(-120); // null
coerceToNaturalNumber(null); // null
```
##### `natural-number/ensure`
If given argument is a natural number coercible value (via [`natural-number/coerce`](#natural-numbercoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureNaturalNumber = require("type/natural-number/ensure");
ensureNaturalNumber(12.93); // "12"
ensureNaturalNumber(-230); // Thrown TypeError: null is not a natural number
```
---
### Plain Object
A _plain object_
- Inherits directly from `Object.prototype` or `null`
- Is not a constructor's `prototype` property
#### `plain-object/is`
Confirms if given object is a _plain object_
```javascript
const isPlainObject = require("type/plain-object/is");
isPlainObject({}); // true
isPlainObject(Object.create(null)); // true
isPlainObject([]); // false
```
#### `plain-object/ensure`
If given argument is a plain object it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensurePlainObject = require("type/plain-object/ensure");
ensurePlainObject({}); // {}
ensureArray("foo"); // Thrown TypeError: foo is not a plain object
```
---
### Array
_Array_ instance
#### `array/is`
Confirms if given object is a native array
```javascript
const isArray = require("type/array/is");
isArray([]); // true
isArray({}); // false
isArray("foo"); // false
```
#### `array/ensure`
If given argument is an array, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureArray = require("type/array/ensure");
ensureArray(["foo"]); // ["foo"]
ensureArray("foo"); // Thrown TypeError: foo is not an array
```
---
#### Array Like
_Array-like_ value (any value with `length` property)
#### `array-like/is`
Restricted _array-like_ confirmation. Returns true for every value that meets following contraints
- is an _object_ (or with `allowString` option, a _string_)
- is not a _function_
- Exposes `length` that meets [`array-length`](#array-lengthcoerce) constraints
```javascript
const isArrayLike = require("type/array-like/is");
isArrayLike([]); // true
isArrayLike({}); // false
isArrayLike({ length: 0 }); // true
isArrayLike("foo"); // false
isArrayLike("foo", { allowString: true }); // true
```
#### `array-like/ensure`
If given argument is an _array-like_, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureArrayLike = require("type/array-like/ensure");
ensureArrayLike({ length: 0 }); // { length: 0 }
ensureArrayLike("foo", { allowString: true }); // "foo"
ensureArrayLike({}); // Thrown TypeError: null is not an iterable
```
---
#### Array length
_number_ primitive that conforms as valid _array length_
##### `array-length/coerce`
Follows [`safe-integer/coerce`](#safe-integercoerce) but returns `null` in place of values which are below `0`
```javascript
const coerceToArrayLength = require("type/safe-integer/coerce");
coerceToArrayLength("12.95"); // 12
coerceToArrayLength(9007199254740992); // null
coerceToArrayLength(null); // null
```
##### `array-length/ensure`
If given argument is an _array length_ coercible value (via [`array-length/coerce`](#array-lengthcoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureArrayLength = require("type/array-length/ensure");
ensureArrayLength(12.93); // "12"
ensureArrayLength(9007199254740992); // Thrown TypeError: null is not a valid array length
```
---
### Iterable
Value which implements _iterable_ protocol
#### `iterable/is`
Confirms if given object is an _iterable_ and is not a _string_ (unless `allowString` option is passed)
```javascript
const isIterable = require("type/iterable/is");
isIterable([]); // true
isIterable({}); // false
isIterable("foo"); // false
isIterable("foo", { allowString: true }); // true
```
Supports also `denyEmpty` option
```javascript
isIterable([], { denyEmpty: true }); // false
isIterable(["foo"], { denyEmpty: true }); // true
```
#### `iterable/ensure`
If given argument is an _iterable_, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureIterable = require("type/iterable/ensure");
ensureIterable([]); // []
ensureIterable("foo", { allowString: true }); // "foo"
ensureIterable({}); // Thrown TypeError: null is not expected iterable
```
Additionally items can be coreced with `coerceItem` option. Note that in this case:
- A newly created array with coerced values is returned
- Validation crashes if any of the items is not coercible
```javascript
ensureIterable(new Set(["foo", 12])); // ["foo", "12"]
ensureIterable(new Set(["foo", {}])); // Thrown TypeError: Set({ "foo", {} }) is not expected iterable
```
---
### Date
_Date_ instance
#### `date/is`
Confirms if given object is a native date, and is not an _Invalid Date_
```javascript
const isDate = require("type/date/is");
isDate(new Date()); // true
isDate(new Date("Invalid date")); // false
isDate(Date.now()); // false
isDate("foo"); // false
```
#### `date/ensure`
If given argument is a date object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureDate = require("type/date/ensure");
const date = new Date();
ensureDate(date); // date
ensureDate(123123); // Thrown TypeError: 123123 is not a date object
```
---
### Time value
_number_ primitive which is a valid _time value_ (as used internally in _Date_ instances)
#### `time-value/coerce`
Follows [`integer/coerce`](#integercoerce) but returns `null` in place of values which go beyond 100 000 0000 days from unix epoch
```javascript
const coerceToTimeValue = require("type/time-value/coerce");
coerceToTimeValue(12312312); // true
coerceToTimeValue(Number.MAX_SAFE_INTEGER); // false
coerceToTimeValue("foo"); // false
```
##### `time-value/ensure`
If given argument is a _time value_ coercible value (via [`time-value/coerce`](#time-valuecoerce)) returns result number.
Otherwise `TypeError` is thrown.
```javascript
const ensureTimeValue = require("type/time-value/ensure");
ensureTimeValue(12.93); // "12"
ensureTimeValue(Number.MAX_SAFE_INTEGER); // Thrown TypeError: null is not a natural number
```
---
### Function
_Function_ instance
#### `function/is`
Confirms if given object is a native function
```javascript
const isFunction = require("type/function/is");
isFunction(function () {}); // true
isFunction(() => {}); // true
isFunction(class {}); // true
isFunction("foo"); // false
```
#### `function/ensure`
If given argument is a function object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureFunction = require("type/function/ensure");
const fn = function () {};
ensureFunction(fn); // fn
ensureFunction(/foo/); // Thrown TypeError: /foo/ is not a function
```
---
#### Plain Function
A _Function_ instance that is not a _Class_
##### `plain-function/is`
Confirms if given object is a _plain function_
```javascript
const isPlainFunction = require("type/plain-function/is");
isPlainFunction(function () {}); // true
isPlainFunction(() => {}); // true
isPlainFunction(class {}); // false
isPlainFunction("foo"); // false
```
##### `plain-function/ensure`
If given argument is a _plain function_ object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensurePlainFunction = require("type/function/ensure");
const fn = function () {};
ensurePlainFunction(fn); // fn
ensurePlainFunction(class {}); // Thrown TypeError: class is not a plain function
```
---
### RegExp
_RegExp_ instance
#### `reg-exp/is`
Confirms if given object is a native regular expression object
```javascript
const isRegExp = require("type/reg-exp/is");
isRegExp(/foo/);
isRegExp({}); // false
isRegExp("foo"); // false
```
#### `reg-exp/ensure`
If given argument is a regular expression object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureRegExp = require("type/reg-exp/ensure");
ensureRegExp(/foo/); // /foo/
ensureRegExp("foo"); // Thrown TypeError: null is not a regular expression object
```
---
### Promise
_Promise_ instance
#### `promise/is`
Confirms if given object is a native _promise_
```javascript
const isPromise = require("type/promise/is");
isPromise(Promise.resolve()); // true
isPromise({ then: () => {} }); // false
isPromise({}); // false
```
##### `promise/ensure`
If given argument is a promise, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensurePromise = require("type/promise/ensure");
const promise = Promise.resolve();
ensurePromise(promise); // promise
eensurePromise({}); // Thrown TypeError: [object Object] is not a promise
```
---
#### Thenable
_Thenable_ object (an object with `then` method)
##### `thenable/is`
Confirms if given object is a _thenable_
```javascript
const isThenable = require("type/thenable/is");
isThenable(Promise.resolve()); // true
isThenable({ then: () => {} }); // true
isThenable({}); // false
```
##### `thenable/ensure`
If given argument is a _thenable_ object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureThenable = require("type/thenable/ensure");
const promise = Promise.resolve();
ensureThenable(promise); // promise
ensureThenable({}); // Thrown TypeError: [object Object] is not a thenable object
```
---
### Error
_Error_ instance
#### `error/is`
Confirms if given object is a native error object
```javascript
const isError = require("type/error/is");
isError(new Error()); // true
isError({ message: "Fake error" }); // false
```
#### `error/ensure`
If given argument is an error object, it is returned back. Otherwise `TypeError` is thrown.
```javascript
const ensureError = require("type/error/ensure");
const someError = new Error("Some error");
ensureError(someError); // someError
ensureError({ message: "Fake error" }); // Thrown TypeError: [object Object] is not an error object
```
---
### Prototype
Some constructor's `prototype` property
#### `prototype/is`
Confirms if given object serves as a _prototype_ property
```javascript
const isPrototype = require("type/prototype/is");
isPrototype({}); // false
isPrototype(Object.prototype); // true
isPrototype(Array.prototype); // true
```
### Tests
$ npm test
[nix-build-image]: https://semaphoreci.com/api/v1/medikoo-org/type/branches/master/shields_badge.svg
[nix-build-url]: https://semaphoreci.com/medikoo-org/type
[win-build-image]: https://ci.appveyor.com/api/projects/status/8nrtluuwsb5k9l8d?svg=true
[win-build-url]: https://ci.appveyor.com/api/project/medikoo/type
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[cov-url]: https://codecov.io/gh/medikoo/type
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[npm-url]: https://www.npmjs.com/package/type