FakerHelpers
Module with various helper methods that transform the method input rather than returning values from locales. The transformation process may call methods that use the locale data.
arrayElement
Returns random element from the given array.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | The type of the entries to pick from. | ||
| array | readonly T[] | ['a', 'b', 'c'] | Array to pick the value from. |
Returns: T
ts
faker.helpers.arrayElement<T>(array: readonly T[] = ['a', 'b', 'c']): T
faker.helpers.arrayElement() // => "b"
faker.helpers.arrayElement(['cat', 'dog', 'mouse']) // 'dog'
arrayElements
Returns a subset with random elements of the given array in random order.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | The type of the entries to pick from. | ||
| array | readonly T[] | ['a', 'b', 'c'] | Array to pick the value from. |
| count? | number | Number of elements to pick. When not provided, random number of elements will be picked. When value exceeds array boundaries, it will be limited to stay inside. |
Returns: T[]
ts
faker.helpers.arrayElements<T>(array: readonly T[] = ['a', 'b', 'c'], count?: number): T[]
faker.helpers.arrayElements() // => ["c","b"]
faker.helpers.arrayElements(['cat', 'dog', 'mouse']) // ['mouse', 'cat']
faker.helpers.arrayElements([1, 2, 3, 4, 5], 2) // [4, 2]
fake
Generator for combining faker methods based on a static string input.
Note: We recommend using string template literals instead of fake(),
which are faster and strongly typed (if you are using TypeScript),
e.g. const address = `${faker.address.zipCode()} ${faker.address.city()}`;
This method is useful if you have to build a random string from a static, non-executable source (e.g. string coming from a user, stored in a database or a file).
It checks the given string for placeholders and replaces them by calling faker methods:
js
const hello = faker.helpers.fake('Hi, my name is {{name.firstName}} {{name.lastName}}!')
This would use the faker.name.firstName() and faker.name.lastName() method to resolve the placeholders respectively.
It is also possible to provide parameters. At first, they will be parsed as json, and if that isn't possible, we will fall back to string:
js
const message = faker.helpers.fake(`You can call me at {{phone.number(+!# !## #### #####!)}}.')
Currently it is not possible to set more than a single parameter.
It is also NOT possible to use any non-faker methods or plain javascript in such templates.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| str | string | The template string that will get interpolated. Must not be empty. |
Returns: string
ts
faker.helpers.fake(str: string): string
faker.helpers.fake('{{name.lastName}}') // 'Barrows'
faker.helpers.fake('{{name.lastName}}, {{name.firstName}} {{name.suffix}}') // 'Durgan, Noe MD'
faker.helpers.fake('This is static test.') // 'This is static test.'
faker.helpers.fake('Good Morning {{name.firstName}}!') // 'Good Morning Estelle!'
faker.helpers.fake('You can call me at {{phone.number(!## ### #####!)}}.') // 'You can call me at 202 555 973722.'
faker.helpers.fake('I flipped the coin and got: {{helpers.arrayElement(["heads", "tails"])}}') // 'I flipped the coin and got: tails'
maybe
Returns the result of the callback if the probability check was successful, otherwise undefined.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | The type of result of the given callback. | ||
| callback | () => T | The callback to that will be invoked if the probability check was successful. | |
| options | { ... } | {} | The options to use. |
| options.probability? | number | 0.5 | The probability ( |
Returns: T
ts
faker.helpers.maybe<T>(callback: () => T, options: {
probability: number
} = {}): T
faker.helpers.maybe(() => 'Hello World!') // 'Hello World!'
faker.helpers.maybe(() => 'Hello World!', { probability: 0.1 }) // undefined
faker.helpers.maybe(() => 'Hello World!', { probability: 0.9 }) // 'Hello World!'
mustache
Replaces the {{placeholder}} patterns in the given string mustache style.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| str | string | The template string to parse. | |
| data | Record<string, (substring: string, args: any[]) => string | string> | The data used to populate the placeholders.
This is a record where the key is the template placeholder,
whereas the value is either a string or a function suitable for |
Returns: string
ts
faker.helpers.mustache(str: string, data: Record<string, (substring: string, args: any[]) => string | string>): string
faker.helpers.mustache() // => ""
faker.helpers.mustache('I found {{count}} instances of "{{word}}".', {
count: () => `${faker.datatype.number()}`,
word: "this word",
}) // 'I found 57591 instances of "this word".'
objectKey
Returns a random key from given object or undefined if no key could be found.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | Record<string, unknown> | Missing | |
| object | T | The object to be used. |
Returns: keyof T
ts
faker.helpers.objectKey<T>(object: T): keyof T
faker.helpers.objectKey({ myProperty: 'myValue' }) // 'myProperty'
objectValue
Returns a random value from given object or undefined if no key could be found.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | Record<string, unknown> | Missing | |
| object | T | The object to be used. |
Returns: T[keyof T]
ts
faker.helpers.objectValue<T>(object: T): T[keyof T]
faker.helpers.objectValue({ myProperty: 'myValue' }) // 'myValue'
regexpStyleStringParse
Replaces the regex like expressions in the given string with matching values.
Supported patterns:
.{times}=> Repeat the character exactlytimestimes..{min,max}=> Repeat the charactermintomaxtimes.[min-max]=> Generate a number between min and max (inclusive).
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| string | string | '' | The template string to to parse. |
Returns: string
ts
faker.helpers.regexpStyleStringParse(string: string = ''): string
faker.helpers.regexpStyleStringParse() // => ""
faker.helpers.regexpStyleStringParse() // ''
faker.helpers.regexpStyleStringParse('#{5}') // '#####'
faker.helpers.regexpStyleStringParse('#{2,9}') // '#######'
faker.helpers.regexpStyleStringParse('[500-15000]') // '8375'
faker.helpers.regexpStyleStringParse('#{3}test[1-5]') // '###test3'
repeatString
Repeats the given string the given number of times.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| string | string | '' | The string to repeat. |
| num | number | 0 | The number of times to repeat it. |
Returns: string
ts
faker.helpers.repeatString(string: string = '', num: number = 0): string
faker.helpers.repeatString() // => ""
faker.helpers.repeatString('Hello world! ') // ''
faker.helpers.repeatString('Hello world! ', 1) // 'Hello world! '
faker.helpers.repeatString('Hello world! ', 2) // 'Hello world! Hello world! '
replaceCreditCardSymbols
Replaces the symbols and patterns in a credit card schema including Luhn checksum.
This method supports both range patterns [4-9] as well as the patterns used by replaceSymbolWithNumber().
L will be replaced with the appropriate Luhn checksum.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| string | string | '6453-####-####-####-###L' | The credit card format pattern. |
| symbol | string | '#' | The symbol to replace with a digit. |
Returns: string
ts
faker.helpers.replaceCreditCardSymbols(string: string = '6453-####-####-####-###L', symbol: string = '#'): string
faker.helpers.replaceCreditCardSymbols() // => "6453-5578-6858-4663-4283"
faker.helpers.replaceCreditCardSymbols() // '6453-4876-8626-8995-3771'
faker.helpers.replaceCreditCardSymbols('1234-[4-9]-##!!-L') // '1234-9-5298-2'
replaceSymbolWithNumber
Parses the given string symbol by symbol and replaces the placeholders with digits (0 - 9).
! will be replaced by digits >=2 (2 - 9).
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| string | string | '' | The template string to parse. |
| symbol | string | '#' | The symbol to replace with digits. |
Returns: string
ts
faker.helpers.replaceSymbolWithNumber(string: string = '', symbol: string = '#'): string
faker.helpers.replaceSymbolWithNumber() // => ""
faker.helpers.replaceSymbolWithNumber() // ''
faker.helpers.replaceSymbolWithNumber('#####') // '04812'
faker.helpers.replaceSymbolWithNumber('!####') // '27378'
faker.helpers.replaceSymbolWithNumber('Your pin is: !####') // '29841'
replaceSymbols
Parses the given string symbol by symbols and replaces the placeholder appropriately.
#will be replaced with a digit (0-9).?will be replaced with an upper letter ('A' - 'Z')- and
*will be replaced with either a digit or letter.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| string | string | '' | The template string to parse. |
Returns: string
ts
faker.helpers.replaceSymbols(string: string = ''): string
faker.helpers.replaceSymbols() // => ""
faker.helpers.replaceSymbols() // ''
faker.helpers.replaceSymbols('#####') // '98441'
faker.helpers.replaceSymbols('?????') // 'ZYRQQ'
faker.helpers.replaceSymbols('*****') // '4Z3P7'
faker.helpers.replaceSymbols('Your pin is: #?*#?*') // '0T85L1'
shuffle
Takes an array and randomizes it in place then returns it.
Uses the modern version of the Fisher–Yates algorithm.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | The type of the entries to shuffle. | ||
| o? | T[] | [] | The array to shuffle. |
Returns: T[]
ts
faker.helpers.shuffle<T>(o?: T[] = []): T[]
faker.helpers.shuffle() // => []
faker.helpers.shuffle() // []
faker.helpers.shuffle(['a', 'b', 'c']) // [ 'b', 'c', 'a' ]
slugify
Slugifies the given string.
For that all spaces ( ) are replaced by hyphens (-)
and most non word characters except for dots and hyphens will be removed.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| string | string | '' | The input to slugify. |
Returns: string
ts
faker.helpers.slugify(string: string = ''): string
faker.helpers.slugify() // => ""
faker.helpers.slugify() // ''
faker.helpers.slugify("Hello world!") // 'Hello-world'
uniqueArray
Takes an array of strings or function that returns a string and outputs a unique array of strings based on that source. This method does not store the unique state between invocations.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| <T> | The type of the entries. | ||
| source | () => T | readonly T[] | The strings to choose from or a function that generates a string. | |
| length | number | The number of elements to generate. |
Returns: T[]
ts
faker.helpers.uniqueArray<T>(source: () => T | readonly T[], length: number): T[]
faker.helpers.uniqueArray() // => []
faker.helpers.uniqueArray(faker.random.word, 50)
faker.helpers.uniqueArray(faker.definitions.name.first_name, 6)
faker.helpers.uniqueArray(["Hello", "World", "Goodbye"], 2)