Array keys in variables in JavaScript

Let's say we have an array like this:

let arr = ['a', 'b', 'c'];

Let's display the element with the key 0:

let arr = ['a', 'b', 'c']; console.log(arr[0]); // shows 'a'

Let's now not write the key of the displayed element directly in square brackets, but write it into a variable:

let arr = ['a', 'b', 'c']; let key = 0; // write the key to a variable

We now use our variable to display the corresponding element:

let arr = ['a', 'b', 'c']; let key = 0; // write the key to a variable console.log(arr[key]); // shows 'a'

Given the following array:

let arr = ['a', 'b', 'c'];

Also given the variable:

let key = 2;

Display the element whose key is stored in the variable key.

Given the following array:

let arr = [1, 2, 3, 4, 5];

Also given the variables:

let key1 = 1; let key2 = 2;

Find the sum of elements whose keys are stored in our variables.

enru