How to Create a Map of Maps in JavaScript

We can create a map of maps in JavaScript by using the Map data structure. This example demonstrates creating a map where both the outer and inner maps use integers for keys and values.

For example,

const outerMap = new Map();

// Populate the inner maps
const innerMap1 = new Map([
    [1, 10],
    [2, 20],
    [3, 30]
]);
const innerMap2 = new Map([
    [4, 40],
    [5, 50],
    [6, 60]
]);

// Insert the inner maps into the outer map
outerMap.set(1, innerMap1);
outerMap.set(2, innerMap2);

// Print the resulting map of maps
console.log('Map of maps with integer keys and values:');
outerMap.forEach((innerMap, outerKey) => {
    console.log(`Outer key: ${outerKey}`);
    innerMap.forEach((value, innerKey) => {
        console.log(`  Inner key: ${innerKey}, value: ${value}`);
    });
});

Map of maps with integer keys and values:
Outer key: 1
  Inner key: 1, value: 10
  Inner key: 2, value: 20
  Inner key: 3, value: 30
Outer key: 2
  Inner key: 4, value: 40
  Inner key: 5, value: 50
  Inner key: 6, value: 60

We can create a map of maps in JavaScript by using the Map data structure. This example demonstrates creating a map where the outer map uses strings for keys and the inner maps use integers for keys and strings for values.

For example,

const outerMap = new Map();

// Populate the inner maps
const innerMap1 = new Map([
    [1, 'one'],
    [2, 'two'],
    [3, 'three']
]);
const innerMap2 = new Map([
    [4, 'four'],
    [5, 'five'],
    [6, 'six']
]);

// Insert the inner maps into the outer map
outerMap.set('first', innerMap1);
outerMap.set('second', innerMap2);

// Print the resulting map of maps
console.log('Map of maps with mixed key and value types:');
outerMap.forEach((innerMap, outerKey) => {
    console.log(`Outer key: ${outerKey}`);
    innerMap.forEach((value, innerKey) => {
        console.log(`  Inner key: ${innerKey}, value: ${value}`);
    });
});

Map of maps with mixed key and value types:
Outer key: first
  Inner key: 1, value: one
  Inner key: 2, value: two
  Inner key: 3, value: three
Outer key: second
  Inner key: 4, value: four
  Inner key: 5, value: five
  Inner key: 6, value: six

We can create a map of maps in JavaScript by using the Map data structure. This example demonstrates creating a map where both the outer and inner maps use strings for keys and doubles for values.

For example,

const outerMap = new Map();

// Populate the inner maps
const innerMap1 = new Map([
    ['A', 1.1],
    ['B', 2.2],
    ['C', 3.3]
]);
const innerMap2 = new Map([
    ['D', 4.4],
    ['E', 5.5],
    ['F', 6.6]
]);

// Insert the inner maps into the outer map
outerMap.set('group1', innerMap1);
outerMap.set('group2', innerMap2);

// Print the resulting map of maps
console.log('Map of maps with string keys and double values:');
outerMap.forEach((innerMap, outerKey) => {
    console.log(`Outer key: ${outerKey}`);
    innerMap.forEach((value, innerKey) => {
        console.log(`  Inner key: ${innerKey}, value: ${value}`);
    });
});

Map of maps with string keys and double values:
Outer key: group1
  Inner key: A, value: 1.1
  Inner key: B, value: 2.2
  Inner key: C, value: 3.3
Outer key: group2
  Inner key: D, value: 4.4
  Inner key: E, value: 5.5
  Inner key: F, value: 6.6