Group a sorted array based on the difference between current and previous elements in JavaScript

Suppose we have an array of Integers sorted in an increasing order like this −

const arr = [ 1, 2, 3, 5, 6, 7, 10, 12, 17, 18];

We are required to write a JavaScript function that takes in one such array. The function should group the array in such a way so that −

• Elements within a group have a difference of 1 or less

• Each group element should have more than one element to be considered valid

Based on the above conditions, the expected output would be −

const output = [
   [1, 2, 3],
   [5, 6, 7],
   [17, 18]
];

Example

The code for this will be −

const arr = [ 1, 2, 3, 5, 6, 7, 10, 12, 17, 18];
const groupNear = (arr = []) => {
   const res = [];
   for (let ind = 0; ind < arr.length; ind++) {
      let value = arr[ind];
      if (arr[ind − 1] + 1 === value) {
         res[res.length − 1].push(value);
      } else if (value + 1 === arr[ind + 1]) {
         res.push([value]);
      };
   };
   return res;
};
console.log(groupNear(arr));

Output

And the output in the console will be −

[ [ 1, 2, 3 ], [ 5, 6, 7 ], [ 17, 18 ] ]