javascript - Group same values in an array within an array in JS

Question

How can I group the same numbers in an array within an array?

I have the following array of numbers:

var arr = [1,1,1,1,2,2,3,3,3,4,5,5,6];

My output should be

[[1,1,1,1],[2,2],[3,3,3],4,[5,5],6]

Answer 1

You could reduce the array and check if the predecessor has the same value and if not take either an array or the value, depending of the next element.

var array = [1, 1, 1, 1, 2, 2, 3, 3, 3, 4, 5, 5, 6],
    grouped = array.reduce((r, v, i, a) => {
        if (v === a[i - 1]) {
            r[r.length - 1].push(v);
        } else {
            r.push(v === a[i + 1] ? [v] : v);
        }
        return r;
    }, []);
    
console.log(grouped);