We have a Map<number,any> like this:

const map1 = new Map();
map1.set(0,'alpha');
map1.set(1,'beta');
map1.set(2,'gamma');
map1.set(3,'omega');
map1.set(4,'theta');

If we delete the entry with index 2 the remaining indexes are [3,4].

We want a function that calculates this result and we want unit tests for it.

Approach

First lets document and implement our function:

Notice that the way we documented our function makes it easy to unit test it. Here’s the unit test. Note that we are testing edge conditions: