/**
* Given an array of number, group algebraic sequences with d=1
* [1,2,3,4,5,6] => true
* [1,2,4,5,6] => false
*/
var arr = [1,2,4,5,6];
const differenceAry = arr.slice(1).map(function(n, i) { return n - arr[i]; })
const isDifference= differenceAry.every(value => value == 1)
console.log(isDifference); // False