Count Groups of Negative Numbers in JavaScript

We have an array of numbers like this −

const arr = [-1,-2,-1,0,-1,-2,-1,-2,-1,0,1,0];

Let’s say, we are required to write a JavaScript function that counts the consecutive groups of negative numbers in the array.

Like here we have consecutive negatives from index 0 to 2 which forms one group and then from 4 to 8 forms the second group

So, for this array, the function should return 2.

Example

Let’s write the code −

const arr = [-1,-2,-1,0,-1,-2,-1,-2,-1,0,1,0];
const countNegativeGroup = arr => {
   return arr.reduce((acc, val, ind) => {
      if(val < 0 && arr[ind+1] >= 0){
         acc++;
      };
      return acc;
   }, 0);
};
console.log(countNegativeGroup(arr));

Output

Following is the output in the console −

2