# Array

A randomly accessible sequence of values of a generic type.

The Array API is very similar to JavaScript's (MDN (opens new window)), with the notable difference that one must make sure that there are no null values if T is a non-nullable reference type. Example:

var arr = new Array<string>(10)
// arr[0]; // would error 😢
for (let i = 0; i < arr.length; ++i) {
  arr[i] = ""
}
arr[0]; // now it works 😊

# Constructor

```
new Array<T>(capacity?: i32)
```
Constructs a new array.

# Static members

```
function isArray(value: U): bool
```
Tests if a value is an array.

# Instance members

# Fields

```
var length: i32
```
The length of this array. Setting the length to a value larger than internal capacity will automatically grow the array.

# Methods

```
function concat(other: Array<T>): Array<T>
```
Concatenates the values of this and the other array to a new array, in this order.
```
function copyWithin(target: i32, start: i32, end?: i32): this
```
Copies a region of an array's values over the respective values starting at the target location.
```
function every(fn: (value: T, index: i32, self: Array<T>) => bool): bool
```
Calls the specified function with every value of the array until it finds the first value for which the function returns false. Returns true if all functions returned true or the array is empty, otherwise false.
```
function fill(value: T, start?: i32, end?: i32): this
```
Replaces the values of the array from start inclusive to end exclusive in place with the specified value, returning the array.
```
function filter(fn: (value: T, index: i32, self: Array<T>) => bool): Array<T>
```
Calls the specified function with every value of the array, returning a new array with all values for which the function returned true.
```
function findIndex(fn: (value: T, index: i32, self: Array<T>) => bool): i32
```
Calls the specified function with every value of the array until it finds the first value for which the function returns true, returning its index. Returns -1 if that's never the case.
```
function findLastIndex(fn: (value: T, index: i32, self: Array<T>) => bool): i32;
```
Calls the specified function with every value of the array starting at the end until it finds the first value for which the function returns true, returning its index. Returns -1 if that's never the case.
```
function flat(): valueof<T>[]
```
Flattens an array of arrays to a one-dimensional array. null entries are ignored.

function forEach(fn: (value: T, index: i32, self: Array<T>) => void): void

Calls the specified function with every value of the array.

```
function includes(value: T, fromIndex?: i32): bool
```
Tests if the array includes the specified value, optionally providing a starting index.
```
function indexOf(value: T, fromIndex?: i32): i32
```
Gets the first index where the specified value can be found in the array. Returns -1 if not found.
```
function join(separator?: string): string
```
Concatenates all values of the array to a string, separated by the specified separator (default: ,).
```
function lastIndexOf(value: T, fromIndex?: i32): i32
```
Gets the last index where the specified value can be found in the array. Returns -1 if not found.
```
function map(fn: (value: T, index: i32, self: Array<T>) => U): Array
```
Calls the specified function with every value of the array, returning a new array of the function's return values.
```
function pop(): T
```
Removes and returns the last value of the array. Modifies Array#length. Throws a RangeError if the array is empty.
```
function push(value: T): i32
```
Adds one more value to the end of the array and returns the Array's new length. Modifies Array#length.
```
function reduce(
 fn: (accumValue: U, currentValue: T, index: i32, self: Array<T>) => U,
 initialValue: U
): U
```
Calls the specified reducer function with each value of the array, resulting in a single return value. The respective previous reducer function's return value is remembered in accumValue, starting with initialValue, becoming the final return value in the process.
```
function reduceRight(
 fn: (accumValue: U, currentValue: T, index: i32, self: Array<T>) => U,
 initialValue: U
): U
```
Calls the specified reducer function with each value of the array, from right to left, resulting in a single return value. See Array#reduce for the reducer function's signature.
```
function reverse(): this
```
Reverses an array's values in place, modifying the array before returning it.
```
function shift(): T
```
Removes and returns the first value of the array. Modifies Array#length.
```
function slice(start?: i32, end?: i32): Array<T>
```
Returns a shallow copy of the array's values from begin inclusive to end exclusive, as a new array. If omitted, end defaults to the end of the array.
```
function some(fn: (value: T, index: i32, self: Array<T>) => bool): bool
```
Calls the specified function with every value of the array until it finds the first value for which the function returns true, returning true. Returns false otherwise or if the array is empty.
```
function sort(fn?: (a: T, b: T) => i32): this
```
Sorts the values of the array in place, using the specified comparator function, modifying the array before returning it. The comparator returning a negative value means a < b, a positive value means a > b and 0 means that both are equal. Unlike in JavaScript, where an implicit conversion to strings is performed, the comparator defaults to compare two values of type T.
```
function splice(start: i32, deleteCount?: i32): Array<T>
```
Removes deleteCount (defaults to all remaining) values from the array, starting at index start, modifying the array in place, returning the removed values.
```
function toString(): string
```
Returns the result of Array#join().
```
function unshift(value: T): i32
```
Adds one more value to the start of the array and returns the Array's new length. Modifies Array#length.

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