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indexOfmethod returns the first index at which a given element can be found in the array, or -1 if it is not present. Counting starts with 0.
let systems = ['Debian', 'Ubuntu', 'Mint']; let i1 = systems.indexOf('Mint'); let i2 = systems.indexOf('Windows');
i1gets the value
i2gets the value
-1. For a complete reference see MDN web docs.
Write a function
addthat adds an element to the end of an array. However, the element should only be added if it is not already in the array.
add([1, 2], 3)should return
[1, 2, 3]and
add([1, 2], 2)should return