How to Determine if One Map Contains All Entries of Another Map in JavaScript?

How can I check if a JavaScript map contains all entries of another map?

// Code Example: 
function mapsContain(mapA, mapB) {
    for (let [key, value] of mapB) {
        if (!mapA.has(key) || mapA.get(key) !== value) {
            return false;
        }
    }
    return true;
}

To check if one JavaScript Map contains all entries of another map, you can iterate through the entries of the second map and verify if each entry exists in the first map with equal key-value pairs.

// Example usage:
let mapA = new Map([['a', 1], ['b', 2]]);
let mapB = new Map([['a', 1]]);
console.log(mapsContain(mapA, mapB)); // true

mapB.set('c', 3);
console.log(mapsContain(mapA, mapB)); // false

Causes

• Comparison of keys alone is insufficient; values must match as well.
• Missing keys or mismatched values will lead to incorrect results.

Solutions

• Use the `has()` method of Map to check for keys.
• Check the equality of values with `get()` method.

Mistake: Checking only keys without values.

Solution: Always verify both the keys and their corresponding values.

Mistake: Using standard object methods instead of Map methods.

Solution: Ensure to use `get()` and `has()` from the Map API.