ArcGIS Arcade Determining if a sorted array of numbers has consecutive numbers within it

Question

I have an array of numbers and want to determine the starting number and ending number of any numbers that are consecutive. The numbers will always be in ascending order.

I would like to create a function that outputs an array which will look like these examples:

[1,2,3,5,6,7] = [[1,3],[5,7]]

[1,2,4,6,7,8,9,10] = [[1,2],[4],[6,10]]

I have made a few meager attempts but I'm just having difficulty with it for whatever reason. I have attempted to adapt this post with no success.

Answer 1

Arcade is heavily influenced by JavaScript, so it is good to look to JavaScript examples when trying to figure out Arcade issues that are non-geospatial in nature. There might be a similar JavaScript example over at StackExchange/StackOverflow, but coming up with a code example was just as quick as searching around those sites.

The following code in Playground | ArcGIS Arcade | ArcGIS Developers,

var arr = [1,2,4,6,7,8,9,10];

var narr = [];
var sarr = [arr[0]];
for(var idx=1; idx < count(arr); idx++) {
    if(arr[idx] == arr[idx-1]+ 1){
        continue;
    } else {
        if(sarr[0] != arr[idx-1]) {
            Insert(sarr, count(sarr), arr[idx-1]);
        }
        Insert(narr, count(narr), sarr);
        var sarr = [arr[idx]];
    }
}
if(sarr[0] != arr[idx-1]) {
    Insert(sarr, count(sarr), arr[idx-1]);
}
Insert(narr, count(narr), sarr);
return narr;

yields,

    [ Array (2) , Array (1) , Array (2) ]

which expands to,

[ [1,2] , [4] , [6,10] ]