collect "alike" elements together into sub-arrays (kinda like a partial reduce, sorta) --- and the second version shows how to not sub-array single elements "easily"

gistfile1.js

function collectLikes(arr) {
	var i, j, type;
	arr = Array.prototype.slice.call(arr);

	for (i=0; i<arr.length; i++) {
		type = typeof arr[i];

		for (j=i+1; j<arr.length; j++) {
			if (typeof arr[j] !== type) {
				break;
			}
		}
		arr.splice(
			/*start=*/i,
			/*howMany=*/j-i,
			/*replace=*/arr.slice(i,j)
		);
	}
	return arr;
}

gistfile2.js

console.log("[ ]",collectLikes([]));
// [ ]
// [ ]

console.log("[ 1 ]",collectLikes([1]));
// [ 1 ]
// [ [ 1 ] ]

console.log("[ 1, 2, 3 ]",collectLikes([1,2,3]));
// [ 1, 2, 3 ]
// [ [ 1, 2, 3 ] ]

console.log("[ 1, 2, '3', '4', '5', 6, true ]",collectLikes([1,2,'3','4','5',6,true]));
// [ 1, 2, '3', '4', '5', 6, true ]
// [ [ 1, 2 ], [ '3', '4', '5' ], [ 6 ], [ true ] ]

console.log("[ 1, '2', 3, true, false, null ]",collectLikes([1,'2',3,true,false,null]));
// [ 1, '2', 3, true, false, null ]
// [ [ 1 ], [ '2' ], [ 3 ], [ true, false ], [ null ] ]

gistfile3.js

function collectLikes(arr) {
	var i, j, type;
	arr = Array.prototype.slice.call(arr);

	for (i=0; i<arr.length; i++) {
		type = typeof arr[i];

		for (j=i+1; j<arr.length; j++) {
			if (typeof arr[j] !== type) {
				break;
			}
		}
		if (j > i + 1) {			// <---- ADDED THIS IF
			arr.splice(
				/*start=*/i,
				/*howMany=*/j-i,
				/*replace=*/arr.slice(i,j)
			);
		}					// <----
	}
	return arr;
}

gistfile4.js

console.log("[ ]",collectLikes([]));
// [ ]
// [ ]

console.log("[ 1 ]",collectLikes([1]));
// [ 1 ]
// [ [ 1 ] ]

console.log("[ 1, 2, 3 ]",collectLikes([1,2,3]));
// [ 1, 2, 3 ]
// [ [ 1, 2, 3 ] ]

console.log("[ 1, 2, '3', '4', '5', 6, true ]",collectLikes([1,2,'3','4','5',6,true]));
// [ 1, 2, '3', '4', '5', 6, true ]
// [ [ 1, 2 ], [ '3', '4', '5' ], 6, true ]

console.log("[ 1, '2', 3, true, false, null ]",collectLikes([1,'2',3,true,false,null]));
// [ 1, '2', 3, true, false, null ]
// [ 1, '2', 3, [ true, false ], null ]