API_REFERENCE.md

API Reference

Table of contents

• Map
  • Constructor
    • from(mapEntries[, mapFn])
    • isMap(x)
    • of(element0[, element1[, ...[, elementN]]])
  • Prototype
    • entry(key)
    • entryOrDefault(key, defaultValue)
    • getOrDefault(key, defaultValue)
    • isEmpty()
    • iter()
    • len()
    • removeEntry(key)
    • toArray()

Map

Constructor

from(mapEntries[, mapFn])

Creates a Map object that contains all key/ value pairs of mapEntries and an optional mapFn to call on every element of the mapEntries.

const entries = [
  [1, 1],
  [2, 2],
];
const m = Map.from(entries, (n) => {
  const k = n[0];
  const v = n[1];

  return [k, 1 + v];
});

m.get(1) === 2;
m.get(2) === 3;

isMap(x)

Returns true if the x is a Map object.

Map.isMap(new Map()) === true;

of(element0[, element1[, ...[, elementN]]])

Creates a new Map object from a variable number of arguments, regardless of the number of type of the arguments.

const m = Map.of([1, 1], [2, 2]);

m.get(1) === 1;
m.get(2) === 2;

Prototype

entry(key)

Gets the given key's corresponding entry in the map, or [key, undefined] if this map contains no mapping for the key.

const m = new Map();

m.set(1, 1);
m.set(2, 2);

m.entry(1); /** [1, 1] */
m.entry(3); /** [3, undefined] */

entryOrDefault(key, defaultValue)

Gets the given key's corresponding entry in the map, or [key, defaultValue] if this map contains no mapping for the key.

const m = new Map();

m.set(1, 1);
m.set(2, 2);

m.entry(1); /** [1, 1] */

getOrDefault(key, defaultValue)

Returns the value to which the specified key is mapped, or defaultValue if this map contains no mapping for the key.

const m = new Map();

'hello world'.split('').filter(Boolean).forEach((n) => {
  const count = 1 + m.getOrDefault(n, 0);

  m.set(n, key);
});

m.get('o') === 2;
m.get('l') === 3;

isEmpty()

Returns true if the map contains no elements.

const m = new Map();

m.isEmpty() === true;

m.set(1, 1);
m.set(2, 2);

m.isEmpty() === false;

iter()

Returns an iterator visiting all key-value pairs.

const m = new Map();

m.set(1, 1);
m.set(2, 2);

const iter = m.iter();

iter.next().value; /** [1, 1] */
iter.next().value; /** [2, 2] */
iter.next().done() === true;

len()

Returns the number of elements in the map.

const m = new Map();

m.len() === 0;

m.set(1, 1);
m.set(2, 2);

m.len() === 2;

removeEntry(key)

Removes the given key from the map, returning the stored key and the value if the key was previously in the map.

const m = new Map();

m.set(1, 1);
m.set(2, 2);

m.removeEntry(1); /** [1, 1] */
m.has(1) === false;

toArray()

Creates an array containing all the elements of the map.

const m = new Map();

m.set(1, 1);
m.set(2, 2);

m.toArray(); /** [[1, 1], [2, 2]] */