# Map

A mapping of generic keys to generic values.

The Map API is very similar to JavaScript's (MDN (opens new window)), with the notable difference that a .get with a key that does not exist results in an error, because undefined cannot be represented. Example:

var map = new Map<i32,string>()

// Because `undefined` cannot be represented if a key is not found, this will error:
var str = map.get(1) // ERROR

// The error can be avoided by first making sure that the key exists, so this works:
var str: string | null = map.has(1) ? map.get(1) : null // OK

# Constructor

```
new Map<K,V>()
```
Constructs a new map mapping keys of type K to values of type V.

# Instance members

# Fields

```
readonly size: i32
```
The current number of key-value pairs in this map.

# Methods

```
function clear(): void
```
Clears the map, deleting all key-value pairs.
```
function delete(key: K): bool
```
Deletes the key-value pair for the corresponding key. Returns true if the key did exist, otherwise false.
```
function get(key: K): V
```
Gets the value corresponding to the specified key. Traps if the key does not exist because "not found" cannot be represented in all cases (use Map#has to check).
```
function has(key: K): bool
```
Tests if the specified key exists.
```
function keys(): Array<K>
```
Gets the keys contained in this map as an array, in insertion order. This is preliminary while iterators are not supported.
```
function set(key: K, value: V): this
```
Sets the value for the specified key. Creates a new key-value pair if the key did not exist.
```
function values(): Array<V>
```
Gets the values contained in this map as an array, in insertion order. This is preliminary while iterators are not supported.
```
function toString(): string
```
Returns a string representation of this map.

← Math Number →