Евгений Петров

function arrSum(array) {
    let sum = 0
    function recur (array){
        if (Array.isArray(array)) {
            array.map(val => {
                
                if(Array.isArray(val)) {
                    recur(val)
                } else {
                    sum += val
                }
            })
        }
    }
    recur(array)
    return sum
}

let arr = [[1, [4,6]], [3, 4], [5, 6]]
let totalSum = arrSum(arr)      \\ => 29