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Interface ReadonlyArray<T, T, T, T>

Type parameters

  • T

  • T

  • T

  • T

Hierarchy

Indexable

[n: number]: T

Index

Properties

length

length: number

Gets the length of the array. This is a number one higher than the highest element defined in an array.

Methods

[Symbol.iterator]

  • Iterator of values in the array.

    Returns IterableIterator<T>

concat

  • Combines two or more arrays.

    Parameters

    • Rest ...items: ConcatArray<T>[]

      Additional items to add to the end of array1.

    Returns T[]

  • Combines two or more arrays.

    Parameters

    • Rest ...items: (T | ConcatArray<T>)[]

      Additional items to add to the end of array1.

    Returns T[]

entries

  • Returns an iterable of key, value pairs for every entry in the array

    Returns IterableIterator<[number, T]>

every

  • every(callbackfn: (value: T, index: number, array: keyof T[]) => unknown, thisArg?: any): boolean
  • Determines whether all the members of an array satisfy the specified test.

    Parameters

    • callbackfn: (value: T, index: number, array: keyof T[]) => unknown

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

        • (value: T, index: number, array: keyof T[]): unknown
        • Parameters

          • value: T
          • index: number
          • array: keyof T[]

          Returns unknown

    • 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 boolean

filter

  • filter<S>(callbackfn: (value: T, index: number, array: keyof T[]) => value is S, thisArg?: any): S[]
  • filter(callbackfn: (value: T, index: number, array: keyof T[]) => unknown, thisArg?: any): T[]
  • Returns the elements of an array that meet the condition specified in a callback function.

    Type parameters

    • S: T

    Parameters

    • callbackfn: (value: T, index: number, array: keyof T[]) => value is S

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

        • (value: T, index: number, array: keyof T[]): value is S
        • Parameters

          • value: T
          • index: number
          • array: keyof T[]

          Returns value is S

    • 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 S[]

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

    Parameters

    • callbackfn: (value: T, index: number, array: keyof T[]) => unknown

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

        • (value: T, index: number, array: keyof T[]): unknown
        • Parameters

          • value: T
          • index: number
          • array: keyof T[]

          Returns unknown

    • 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 T[]

find

  • find<S>(predicate: (this: void, value: T, index: number, obj: keyof T[]) => value is S, thisArg?: any): S | undefined
  • find(predicate: (value: T, index: number, obj: keyof T[]) => unknown, thisArg?: any): T | undefined
  • Returns the value of the first element in the array where predicate is true, and undefined otherwise.

    Type parameters

    • S: T

    Parameters

    • predicate: (this: void, value: T, index: number, obj: keyof T[]) => value is S

      find calls predicate once for each element of the array, in ascending order, until it finds one where predicate returns true. If such an element is found, find immediately returns that element value. Otherwise, find returns undefined.

        • (this: void, value: T, index: number, obj: keyof T[]): value is S
        • Parameters

          • this: void
          • value: T
          • index: number
          • obj: keyof T[]

          Returns value is S

    • Optional thisArg: any

      If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.

    Returns S | undefined

  • Parameters

    • predicate: (value: T, index: number, obj: keyof T[]) => unknown
        • (value: T, index: number, obj: keyof T[]): unknown
        • Parameters

          • value: T
          • index: number
          • obj: keyof T[]

          Returns unknown

    • Optional thisArg: any

    Returns T | undefined

findIndex

  • findIndex(predicate: (value: T, index: number, obj: keyof T[]) => unknown, thisArg?: any): number
  • Returns the index of the first element in the array where predicate is true, and -1 otherwise.

    Parameters

    • predicate: (value: T, index: number, obj: keyof T[]) => unknown

      find calls predicate once for each element of the array, in ascending order, until it finds one where predicate returns true. If such an element is found, findIndex immediately returns that element index. Otherwise, findIndex returns -1.

        • (value: T, index: number, obj: keyof T[]): unknown
        • Parameters

          • value: T
          • index: number
          • obj: keyof T[]

          Returns unknown

    • Optional thisArg: any

      If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.

    Returns number

forEach

  • forEach(callbackfn: (value: T, index: number, array: keyof T[]) => void, thisArg?: any): void
  • Performs the specified action for each element in an array.

    Parameters

    • callbackfn: (value: T, index: number, array: keyof T[]) => void

      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: keyof T[]): void
        • Parameters

          • value: T
          • index: number
          • array: keyof T[]

          Returns void

    • 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

includes

  • includes(searchElement: T, fromIndex?: undefined | number): boolean
  • Determines whether an array includes a certain element, returning true or false as appropriate.

    Parameters

    • searchElement: T

      The element to search for.

    • Optional fromIndex: undefined | number

      The position in this array at which to begin searching for searchElement.

    Returns boolean

indexOf

  • indexOf(searchElement: T, fromIndex?: undefined | number): number
  • Returns the index of the first occurrence of a value in an array.

    Parameters

    • searchElement: T

      The value to locate in the array.

    • Optional fromIndex: undefined | 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?: undefined | string): string
  • Adds all the elements of an array separated by the specified separator string.

    Parameters

    • Optional separator: undefined | string

      A string used to separate one element of an array from the next in the resulting String. If omitted, the array elements are separated with a comma.

    Returns string

keys

  • Returns an iterable of keys in the array

    Returns IterableIterator<number>

lastIndexOf

  • lastIndexOf(searchElement: T, fromIndex?: undefined | number): number
  • Returns the index of the last occurrence of a specified value in an array.

    Parameters

    • searchElement: T

      The value to locate in the array.

    • Optional fromIndex: undefined | number

      The array index at which to begin the search. If fromIndex is omitted, the search starts at the last index in the array.

    Returns number

map

  • map<U>(callbackfn: (value: T, index: number, array: keyof T[]) => U, thisArg?: any): U[]
  • Calls a defined callback function on each element of an array, and returns an array that contains the results.

    Type parameters

    • U

    Parameters

    • callbackfn: (value: T, index: number, array: keyof T[]) => U

      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: keyof T[]): U
        • Parameters

          • value: T
          • index: number
          • array: keyof T[]

          Returns U

    • 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[]

reduce

  • reduce(callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T): T
  • reduce(callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T, initialValue: T): T
  • reduce<U>(callbackfn: (previousValue: U, currentValue: T, currentIndex: number, array: keyof T[]) => U, initialValue: U): U
  • 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: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T

      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: keyof T[]): T
        • Parameters

          • previousValue: T
          • currentValue: T
          • currentIndex: number
          • array: keyof T[]

          Returns T

    Returns T

  • Parameters

    • callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T
        • (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]): T
        • Parameters

          • previousValue: T
          • currentValue: T
          • currentIndex: number
          • array: keyof T[]

          Returns T

    • initialValue: T

    Returns T

  • 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: (previousValue: U, currentValue: T, currentIndex: number, array: keyof T[]) => U

      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: keyof T[]): U
        • Parameters

          • previousValue: U
          • currentValue: T
          • currentIndex: number
          • array: keyof T[]

          Returns U

    • 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: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T): T
  • reduceRight(callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T, initialValue: T): T
  • reduceRight<U>(callbackfn: (previousValue: U, currentValue: T, currentIndex: number, array: keyof T[]) => U, initialValue: U): U
  • 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: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T

      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: keyof T[]): T
        • Parameters

          • previousValue: T
          • currentValue: T
          • currentIndex: number
          • array: keyof T[]

          Returns T

    Returns T

  • Parameters

    • callbackfn: (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]) => T
        • (previousValue: T, currentValue: T, currentIndex: number, array: keyof T[]): T
        • Parameters

          • previousValue: T
          • currentValue: T
          • currentIndex: number
          • array: keyof T[]

          Returns T

    • initialValue: T

    Returns T

  • 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: (previousValue: U, currentValue: T, currentIndex: number, array: keyof T[]) => U

      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: keyof T[]): U
        • Parameters

          • previousValue: U
          • currentValue: T
          • currentIndex: number
          • array: keyof T[]

          Returns U

    • 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

slice

  • slice(start?: undefined | number, end?: undefined | number): T[]
  • Returns a section of an array.

    Parameters

    • Optional start: undefined | number

      The beginning of the specified portion of the array.

    • Optional end: undefined | number

      The end of the specified portion of the array. This is exclusive of the element at the index 'end'.

    Returns T[]

some

  • some(callbackfn: (value: T, index: number, array: keyof T[]) => unknown, thisArg?: any): boolean
  • Determines whether the specified callback function returns true for any element of an array.

    Parameters

    • callbackfn: (value: T, index: number, array: keyof T[]) => unknown

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

        • (value: T, index: number, array: keyof T[]): unknown
        • Parameters

          • value: T
          • index: number
          • array: keyof T[]

          Returns unknown

    • 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 boolean

toLocaleString

  • toLocaleString(): string
  • Returns a string representation of an array. The elements are converted to string using their toLocalString methods.

    Returns string

toString

  • toString(): string
  • Returns a string representation of an array.

    Returns string

values

  • Returns an iterable of values in the array

    Returns IterableIterator<T>