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Get element's position in array given a key-value pair

Say we have an array of questions, each of which are objects with this structure:

    id: 0,
    type: 'datastructure',
    category: 'Array',
    concept: 'Average Access Time',
    complexity: 'Θ(1)'

And say elements in the array are ordered, such that object at position 0 has id: 0, object at position 1 has id: 1, etc.

Then if we need to know the index in the array for element with id: 42 it's pretty obvious that it's just 42. But if we don't want to rely on objects being ordered (or if we want to search using a different key-value pair), the way to get that index is as follows:

const index = =>;

That is, we use map() to specify which key-value pair we will be taking into account and then indexOf() to find the index for our element.