How to convert an array into a complex array JavaScript?

Let’s say, we are required to write a function that takes in an array of Numbers and number n, where n >= any number of the array. The function is required to break the array into subarrays if the sum of consecutive elements of the array exceeds the number n.

For example −

// if the original array is:
const arr = [2, 1, 2, 1, 1, 1, 1, 1];
// and the number n is 4
// then the output array should be:
const output = [ [ 2, 1 ], [ 2, 1, 1 ], [ 1, 1, 1 ] ];

Let’s write the code for this function −

Example

const arr = [2, 1, 2, 1, 1, 1, 1, 1];
const splitArray = (arr, num) => {
   return arr.reduce((acc, val, ind) => {
      let { sum, res } = acc;
      if(ind === 0){
         return {sum: val, res:[[val]]};
      };
      if(sum + val <= num){
         res[res.length-1].push(val);
         sum +=val;
      }else{
         res.push([val]);
         sum = val;
      };
      return { sum, res };
   }, {
      sum: 0,
      res: []
   }).res;
};
console.log(splitArray(arr, 4));
console.log(splitArray(arr, 5));

Output

The output in the console will be −

[ [ 2, 1 ], [ 2, 1, 1 ], [ 1, 1, 1 ] ]
[ [ 2, 1, 2 ], [ 1, 1, 1, 1, 1 ] ]