7kyu-finding-length-of-the-sequence.js

// As part of this Kata, you need to find the length of the sequence in an array, between the first and the second occurrence of a specified number.

// For example, for a given array arr

// [0, -3, 7, 4, 0, 3, 7, 9]

// Finding length between two 7s like

// `lengthOfSequence([0, -3, 7, 4, 0, 3, 7, 9], 7)`

// would return 5.

// For sake of simplicity, there will only be numbers (positive or negative) in the supplied array.

// If there are less or more than two occurances of the number to searched for, return 0.

const lengthOfSequence = function(arr, n) {
        const onlyN = arr.filter(value => value === n);
        if (onlyN.length !== 2) {
                return 0;
        }
        return arr.lastIndexOf(n) - arr.indexOf(n) + 1;
};