Class Map
Map objects are collections of key/value pairs where both the keys and values may be arbitrary ECMAScript language values. A distinct key value may only occur in one key/value pair within the Map's collection. Key/value pairs are stored and iterated in insertion order.
API Version:
Available from version 21.2.
| Property | Description |
|---|---|
| size: Number | Number of key/value pairs stored in this map. |
| Constructor | Description |
|---|---|
| Map() | Creates an empty map. |
| Map(Iterable) | If the passed value is null or undefined then an empty map is constructed. |
| Method | Description |
|---|---|
| clear() | Removes all key/value pairs from this map. |
| delete(Object) | Removes the entry for the given key. |
| entries() | Returns an iterator containing all key/value pairs of this map. |
| forEach(Function) | Runs the provided callback function once for each key/value pair present in this map. |
| forEach(Function, Object) | Runs the provided callback function once for each key/value pair present in this map. |
| get(Object) | Returns the value associated with the given key. |
| has(Object) | Returns if this map has value associated with the given key. |
| keys() | Returns an iterator containing all keys of this map. |
| set(Object, Object) | Adds or updates a key/value pair to the map. |
| values() | Returns an iterator containing all values of this map. |
assign, create, create, defineProperties, defineProperty, entries, freeze, fromEntries, getOwnPropertyDescriptor, getOwnPropertyNames, getOwnPropertySymbols, getPrototypeOf, hasOwnProperty, is, isExtensible, isFrozen, isPrototypeOf, isSealed, keys, preventExtensions, propertyIsEnumerable, seal, setPrototypeOf, toLocaleString, toString, valueOf, values
- size: Number
Number of key/value pairs stored in this map.
- Map()
Creates an empty map.
- Map(values: Iterable)
If the passed value is null or undefined then an empty map is constructed. Else an iterator object is expected that produces a two element array-like object whose first element is a value that will be used as a Map key and whose second element is the value to associate with that key.
Parameters:
- values - The initial map values
- clear(): void
Removes all key/value pairs from this map.
- delete(key: Object): Boolean
Removes the entry for the given key.
Parameters:
- key - The key of the key/value pair to be removed from the map.
Returns:
trueif the map contained an entry for the passed key that was removed. Elsefalseis returned.
- entries(): ES6Iterator
Returns an iterator containing all key/value pairs of this map. The iterator produces a series of two-element arrays with the first element as the key and the second element as the value.
- forEach(callback: Function): void
Runs the provided callback function once for each key/value pair present in this map.
Parameters:
- callback - The function to call, which is invoked with three arguments: the value of the element, the key of the element, and the Map object being iterated.
- forEach(callback: Function, thisObject: Object): void
Runs the provided callback function once for each key/value pair present in this map.
Parameters:
- callback - The function to call, which is invoked with three arguments: the value of the element, the key of the element, and the Map object being iterated.
- thisObject - The Object to use as 'this' when executing callback.
- get(key: Object): Object
Returns the value associated with the given key.
Parameters:
- key - The key to look for.
Returns:
- The value associated with the given key if an entry with the key exists else
undefinedis returned.
- has(key: Object): Boolean
Returns if this map has value associated with the given key.
Parameters:
- key - The key to look for.
Returns:
trueif an entry with the key exists elsefalseis returned.
- keys(): ES6Iterator
Returns an iterator containing all keys of this map.
- set(key: Object, value: Object): Map
Adds or updates a key/value pair to the map.
You can't use JavaScript bracket notation to access map entries. JavaScript bracket notation accesses only properties for Map objects, not map entries.
Parameters:
- key - The key object.
- value - The value to be associated with the key.
Returns:
- This map object.
- values(): ES6Iterator
Returns an iterator containing all values of this map.