Addition multiplication ladder in an array in JavaScriptn

We are required to write a JavaScript function that takes in an array of numbers and returns the alternative multiplicative sum of the elements.

For example: If the array is −

const arr = [1, 2, 3, 4, 5, 6, 7];

Then the output should be calculated like this −

1*2+3*4+5*6+7
2+12+30+7

And the output should be −

51

Let’s write the code for this function −

Example

The code for this will be −

const arr = [1, 2, 3, 4, 5, 6, 7];
const alternateOperation = arr => {
   const productArr = arr.reduce((acc, val, ind) => {
      if(ind % 2 === 1){
         return acc;
      };
      acc.push(val * (arr[ind + 1] || 1));
      return acc;
   }, []);
   return productArr.reduce((acc, val) => acc + val);
};
console.log(alternateOperation(arr));

Output

The output in the console −

51