Maybe

Validates if value is nil or matches expectation.

example

import { expect } from 'chai';

import { maybe, Maybe, PropTypes, ValidationError, validate } from 'typend';

validate(undefined, PropTypes.maybe(String));

validate(null, PropTypes.maybe(String));

validate('foo', PropTypes.maybe(String));

validate('foo', new Maybe(String));

expect(() => validate('foo', maybe('baz'))).to.throw(ValidationError);

Type parameters

▪ T

▪ T

Hierarchy

↳ WrapperPattern

• WrapperPattern

  ↳ Maybe

Implements

• Pattern
• Pattern

Indexable

• [ n: number]: T

Validates if value is nil or matches expectation.

example

import { expect } from 'chai';

import { maybe, Maybe, PropTypes, ValidationError, validate } from 'typend';

validate(undefined, PropTypes.maybe(String));

validate(null, PropTypes.maybe(String));

validate('foo', PropTypes.maybe(String));

validate('foo', new Maybe(String));

expect(() => validate('foo', maybe('baz'))).to.throw(ValidationError);

Index

Constructors

• constructor

Properties

• length
• describer
• kind

Accessors

• isOptional
• isRequired

Methods

• concat
• describe
• every
• filter
• forEach
• getInitializer
• getKind
• hasInitializer
• indexOf
• join
• lastIndexOf
• map
• onValidation
• pop
• push
• reduce
• reduceRight
• reverse
• setInitializer
• shift
• slice
• some
• sort
• splice
• toLocaleString
• toString
• unshift
• getDescriber
• setDescriber

Constructors

constructor

+ new Maybe(...expectations: any[]): Maybe

Inherited from WrapperPattern.constructor

Overrides void

Parameters:

Name	Type
...expectations	any[]

Returns: Maybe

Properties

length

• length: number

Inherited from Optional.length

Overrides Optional.length

Gets or sets the length of the array. This is a number one higher than the highest index in the array.

---

Static describer

▪ describer: Describer

Inherited from WrapperPattern.describer

Overrides void

---

Static kind

▪ kind: KINDS = KINDS.MAYBE

Overrides WrapperPattern.kind

Accessors

isOptional

• get isOptional(): Optional

Inherited from WrapperPattern.isOptional

Overrides void

Returns: Optional

---

isRequired

• get isRequired(): any

Inherited from WrapperPattern.isRequired

Overrides void

Returns: any

Methods

concat

▸ concat(...items: ConcatArray‹T›[]): T[]

Inherited from Optional.concat

Overrides Optional.concat

Combines two or more arrays. This method returns a new array without modifying any existing arrays.

Parameters:

Name	Type	Description
...items	ConcatArray‹T›[]	Additional arrays and/or items to add to the end of the array.

Returns: T[]

▸ concat(...items: T | ConcatArray‹T›[]): T[]

Inherited from Optional.concat

Overrides Optional.concat

Combines two or more arrays. This method returns a new array without modifying any existing arrays.

Parameters:

Name	Type	Description
...items	T | ConcatArray‹T›[]	Additional arrays and/or items to add to the end of the array.

Returns: T[]

---

describe

▸ describe(value: any): string

Inherited from WrapperPattern.describe

Overrides void

Parameters:

Name	Type
value	any

Returns: string

---

every

▸ every‹S›(predicate: function, thisArg?: any): this is S[]

Inherited from Optional.every

Overrides Optional.every

Determines whether all the members of an array satisfy the specified test.

Type parameters:

▪ S: T

Parameters:

▪ predicate: function

A function that accepts up to three arguments. The every method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value false, or until the end of the array.

▸ (value: T, index: number, array: T[]): value is S

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

Returns: this is S[]

▸ every(predicate: function, thisArg?: any): boolean

Inherited from Optional.every

Overrides Optional.every

Determines whether all the members of an array satisfy the specified test.

Parameters:

▪ predicate: function

A function that accepts up to three arguments. The every method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value false, or until the end of the array.

▸ (value: T, index: number, array: T[]): unknown

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

Returns: boolean

---

filter

▸ filter‹S›(predicate: function, thisArg?: any): S[]

Inherited from Optional.filter

Overrides Optional.filter

Returns the elements of an array that meet the condition specified in a callback function.

Type parameters:

▪ S: T

Parameters:

▪ predicate: function

A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.

▸ (value: T, index: number, array: T[]): value is S

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

Returns: S[]

▸ filter(predicate: function, thisArg?: any): T[]

Inherited from Optional.filter

Overrides Optional.filter

Returns the elements of an array that meet the condition specified in a callback function.

Parameters:

▪ predicate: function

A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.

▸ (value: T, index: number, array: T[]): unknown

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

Returns: T[]

---

forEach

▸ forEach(callbackfn: function, thisArg?: any): void

Inherited from Optional.forEach

Overrides Optional.forEach

Performs the specified action for each element in an array.

Parameters:

▪ callbackfn: function

A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.

▸ (value: T, index: number, array: T[]): void

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

Returns: void

---

getInitializer

▸ getInitializer(): any | undefined

Implementation of Pattern

Inherited from WrapperPattern.getInitializer

Overrides void

Returns: any | undefined

---

getKind

▸ getKind(): string

Implementation of Pattern

Inherited from WrapperPattern.getKind

Overrides void

Returns: string

---

hasInitializer

▸ hasInitializer(): boolean

Implementation of Pattern

Inherited from WrapperPattern.hasInitializer

Overrides void

Returns: boolean

---

indexOf

▸ indexOf(searchElement: T, fromIndex?: number): number

Inherited from Optional.indexOf

Overrides Optional.indexOf

Returns the index of the first occurrence of a value in an array, or -1 if it is not present.

Parameters:

Name	Type	Description
searchElement	T	The value to locate in the array.
fromIndex?	number	The array index at which to begin the search. If fromIndex is omitted, the search starts at index 0.

Returns: number

---

join

▸ join(separator?: string): string

Inherited from Optional.join

Overrides Optional.join

Adds all the elements of an array into a string, separated by the specified separator string.

Parameters:

Name	Type	Description
separator?	string	A string used to separate one element of the array from the next in the resulting string. If omitted, the array elements are separated with a comma.

Returns: string

---

lastIndexOf

▸ lastIndexOf(searchElement: T, fromIndex?: number): number

Inherited from Optional.lastIndexOf

Overrides Optional.lastIndexOf

Returns the index of the last occurrence of a specified value in an array, or -1 if it is not present.

Parameters:

Name	Type	Description
searchElement	T	The value to locate in the array.
fromIndex?	number	The array index at which to begin searching backward. If fromIndex is omitted, the search starts at the last index in the array.

Returns: number

---

map

▸ map‹U›(callbackfn: function, thisArg?: any): U[]

Inherited from Optional.map

Overrides Optional.map

Calls a defined callback function on each element of an array, and returns an array that contains the results.

Type parameters:

▪ U

Parameters:

▪ callbackfn: function

A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.

▸ (value: T, index: number, array: T[]): U

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

Returns: U[]

---

onValidation

▸ onValidation(...expectations: any[]): boolean

Inherited from WrapperPattern.onValidation

Overrides void

Parameters:

Name	Type
...expectations	any[]

Returns: boolean

---

pop

▸ pop(): T | undefined

Inherited from Optional.pop

Overrides Optional.pop

Removes the last element from an array and returns it. If the array is empty, undefined is returned and the array is not modified.

Returns: T | undefined

---

push

▸ push(...items: T[]): number

Inherited from Optional.push

Overrides Optional.push

Appends new elements to the end of an array, and returns the new length of the array.

Parameters:

Name	Type	Description
...items	T[]	New elements to add to the array.

Returns: number

---

reduce

▸ reduce(callbackfn: function): T

Inherited from Optional.reduce

Overrides Optional.reduce

Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

Parameters:

▪ callbackfn: function

A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.

▸ (previousValue: T, currentValue: T, currentIndex: number, array: T[]): T

Parameters:

Name	Type
previousValue	T
currentValue	T
currentIndex	number
array	T[]

Returns: T

▸ reduce(callbackfn: function, initialValue: T): T

Inherited from Optional.reduce

Overrides Optional.reduce

Parameters:

▪ callbackfn: function

▸ (previousValue: T, currentValue: T, currentIndex: number, array: T[]): T

Parameters:

Name	Type
previousValue	T
currentValue	T
currentIndex	number
array	T[]

▪ initialValue: T

Returns: T

▸ reduce‹U›(callbackfn: function, initialValue: U): U

Inherited from Optional.reduce

Overrides Optional.reduce

Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

Type parameters:

▪ U

Parameters:

▪ callbackfn: function

A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.

▸ (previousValue: U, currentValue: T, currentIndex: number, array: T[]): U

Parameters:

Name	Type
previousValue	U
currentValue	T
currentIndex	number
array	T[]

▪ initialValue: U

If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.

Returns: U

---

reduceRight

▸ reduceRight(callbackfn: function): T

Inherited from Optional.reduceRight

Overrides Optional.reduceRight

Calls the specified callback function for all the elements in an array, in descending order. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

Parameters:

▪ callbackfn: function

A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.

▸ (previousValue: T, currentValue: T, currentIndex: number, array: T[]): T

Parameters:

Name	Type
previousValue	T
currentValue	T
currentIndex	number
array	T[]

Returns: T

▸ reduceRight(callbackfn: function, initialValue: T): T

Inherited from Optional.reduceRight

Overrides Optional.reduceRight

Parameters:

▪ callbackfn: function

▸ (previousValue: T, currentValue: T, currentIndex: number, array: T[]): T

Parameters:

Name	Type
previousValue	T
currentValue	T
currentIndex	number
array	T[]

▪ initialValue: T

Returns: T

▸ reduceRight‹U›(callbackfn: function, initialValue: U): U

Inherited from Optional.reduceRight

Overrides Optional.reduceRight

Calls the specified callback function for all the elements in an array, in descending order. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

Type parameters:

▪ U

Parameters:

▪ callbackfn: function

A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.

▸ (previousValue: U, currentValue: T, currentIndex: number, array: T[]): U

Parameters:

Name	Type
previousValue	U
currentValue	T
currentIndex	number
array	T[]

▪ initialValue: U

If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.

Returns: U

---

reverse

▸ reverse(): T[]

Inherited from Optional.reverse

Overrides Optional.reverse

Reverses the elements in an array in place. This method mutates the array and returns a reference to the same array.

Returns: T[]

---

setInitializer

▸ setInitializer(initializer: any): void

Implementation of Pattern

Inherited from WrapperPattern.setInitializer

Overrides void

Parameters:

Name	Type
initializer	any

Returns: void

---

shift

▸ shift(): T | undefined

Inherited from Optional.shift

Overrides Optional.shift

Removes the first element from an array and returns it. If the array is empty, undefined is returned and the array is not modified.

Returns: T | undefined

---

slice

▸ slice(start?: number, end?: number): T[]

Inherited from Optional.slice

Overrides Optional.slice

Returns a copy of a section of an array. For both start and end, a negative index can be used to indicate an offset from the end of the array. For example, -2 refers to the second to last element of the array.

Parameters:

Name	Type	Description
start?	number	The beginning index of the specified portion of the array. If start is undefined, then the slice begins at index 0.
end?	number	The end index of the specified portion of the array. This is exclusive of the element at the index 'end'. If end is undefined, then the slice extends to the end of the array.

Returns: T[]

---

some

▸ some(predicate: function, thisArg?: any): boolean

Inherited from Optional.some

Overrides Optional.some

Determines whether the specified callback function returns true for any element of an array.

Parameters:

▪ predicate: function

A function that accepts up to three arguments. The some method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value true, or until the end of the array.

▸ (value: T, index: number, array: T[]): unknown

Parameters:

Name	Type
value	T
index	number
array	T[]

▪Optional thisArg: any

An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

Returns: boolean

---

sort

▸ sort(compareFn?: function): this

Inherited from Optional.sort

Overrides Optional.sort

Sorts an array in place. This method mutates the array and returns a reference to the same array.

Parameters:

▪Optional compareFn: function

Function used to determine the order of the elements. It is expected to return a negative value if the first argument is less than the second argument, zero if they're equal, and a positive value otherwise. If omitted, the elements are sorted in ascending, ASCII character order.

[11,2,22,1].sort((a, b) => a - b)

▸ (a: T, b: T): number

Parameters:

Name	Type
a	T
b	T

Returns: this

---

splice

▸ splice(start: number, deleteCount?: number): T[]

Inherited from Optional.splice

Overrides Optional.splice

Removes elements from an array and, if necessary, inserts new elements in their place, returning the deleted elements.

Parameters:

Name	Type	Description
start	number	The zero-based location in the array from which to start removing elements.
deleteCount?	number	The number of elements to remove.

Returns: T[]

An array containing the elements that were deleted.

▸ splice(start: number, deleteCount: number, ...items: T[]): T[]

Inherited from Optional.splice

Overrides Optional.splice

Removes elements from an array and, if necessary, inserts new elements in their place, returning the deleted elements.

Parameters:

Name	Type	Description
start	number	The zero-based location in the array from which to start removing elements.
deleteCount	number	The number of elements to remove.
...items	T[]	Elements to insert into the array in place of the deleted elements.

Returns: T[]

An array containing the elements that were deleted.

---

toLocaleString

▸ toLocaleString(): string

Inherited from Optional.toLocaleString

Overrides Optional.toLocaleString

Returns a string representation of an array. The elements are converted to string using their toLocaleString methods.

Returns: string

---

toString

▸ toString(): string

Inherited from Optional.toString

Overrides Optional.toString

Returns a string representation of an array.

Returns: string

---

unshift

▸ unshift(...items: T[]): number

Inherited from Optional.unshift

Overrides Optional.unshift

Inserts new elements at the start of an array, and returns the new length of the array.

Parameters:

Name	Type	Description
...items	T[]	Elements to insert at the start of the array.

Returns: number

---

Static getDescriber

▸ getDescriber(): Describer

Inherited from WrapperPattern.getDescriber

Overrides void

Returns: Describer

---

Static setDescriber

▸ setDescriber(describer: Describer): void

Inherited from WrapperPattern.setDescriber

Overrides void

Parameters:

Name	Type
describer	Describer

Returns: void