Iterating over a map

1 minute read

Iterate over map entries as key,value tuples.

const map = new Map([
  ["a", 1],
  ["b", 2],
  ["c", 3],
]);

for (const entry of map) {
  console.log(entry);
}
  

[ "a", 1 ]
[ "b", 2 ]
[ "c", 3 ]

Iterate over the map, accessing the key and value parts as variables.

const map = new Map([["a", 1], ["b", 2], ["c", 3]]);

for (const [k, v] of map) {
  console.log(`key: ${k} => value: ${v}`);
}
  

key: a => value: 1
key: b => value: 2
key: c => value: 3

Iterate over just keys.

const map = new Map([["a", 1], ["b", 2], ["c", 3]]);

for (const [key] of map) {
  console.log(`key: ${key}`);
}
  

key: a
key: b
key: c

Iterate over just the values. Note that a placeholder is required for each key, as designated by the underscore (_).

const map = new Map([["a", 1], ["b", 2], ["c", 3]]);

for (const [_, value] of map) {
  console.log(`value: ${value}`);
}
  

value: 1
value: 2
value: 3