Javascript : Find the missing number in array of consequative numbers

 

In array of consequative numbers find missing number.

Code:

    const arr =[2,3,4,6,7]

    //1 , 2 , 3, 4, 5 , 6

    function findMissing(arr){

        let n = arr.length +1 //expected numbers in array including one missing

        let min = Math.min(...arr);

        let max = min + n -1 ;//expectd max

        let expectedSum = ((min + max) *n)/2

        let actualSum = arr.reduce((acc,item)=>{ return acc+item},0)

        return expectedSum -actualSum

    }

    let result = findMissing(arr)

    console.log(`Missing no=${result}`)

Output:

Missing no=5