How can I verify if two JavaScript Map objects have identical key sets?

Other Questions JavaScript
1

In JavaScript, how can you verify that two Map objects share identical keys? For example, maps with keys ‘alpha’ and ‘beta’ match, while an extra key indicates a difference.

const mapOne = new Map();
mapOne.set('alpha', 10);
mapOne.set('beta', 20);

const mapTwo = new Map();
mapTwo.set('beta', 30);
mapTwo.set('alpha', 40);

const mapExtra = new Map();
mapExtra.set('alpha', 50);
mapExtra.set('beta', 60);
mapExtra.set('gamma', 70);
2

try comparing the sizes then looping through one map’s keys to see if the other map contains them. if a key’s missing, they differ. not the most fancy solution but it works!

3

Based on my experience, the most straightforward way is to compare their sizes first and then check for each key in one map whether it exists in the other. For instance, by iterating over the keys of one map and using the has method on the other, you can confirm if both include exactly the same keys. This approach not only handles cases with keys in different orders but is also effective in spotting an extra or missing key. Although it may seem basic, this method reliably works in practice and is easy to understand and debug in larger applications.

4

In my projects, a different approach I have adopted starts by comparing the sizes of the two maps and then using an iterator from one of them to construct a reference object with keys as properties. I then check every key from the second map against this object. This technique works well, especially when dealing with maps that may contain non-primitive keys, by converting them to a consistent format before comparison. I find that this method not only serves as a fail-fast mechanism but also makes isolating the missing or additional key much simpler during debugging.

5

An alternative method that has worked well for me involves converting the map keys into sorted arrays and then comparing these arrays as strings. This approach uses Array.from to extract the keys and then sorts them. It simplifies debugging since you can see exactly where the differences lie if the maps are not equal. Although this method adds a bit of overhead with sorting, it reliably handles cases with unordered keys and provides clear evidence of mismatches, which can be very helpful during development.

6

i’d give a try to making a set of one map’s keys and then looping thru the other while checking for membership after comparing lengths. it’s a concise method and realy easy to spot subtle key mismatches.