Find the perimeter or area of a polygon from a set of points

area.js

/**
 * area(Array<Array<Number>> ...list)
 *
 * takes in a set of points (in clockwise or counterclockwise order) and returns the area of the polygon the points form
 * example call: `area([3, 10], [9, 7], [11, 2], [2, 2]);`
**/

function area(...list) {
  let total = 0;
  for (let index = 0; index < list.length; index++) {
    const point = list[index];
    let nextPoint = list[index+1];
    nextPoint ??= list[0];
    total += (point[0] * nextPoint[1] - point[1] * nextPoint[0]);
  }
  return Math.round(Math.abs(total/2) * 100)/100;
}

area([3, 10], [9, 7], [11, 2], [2, 2]); // 48

perim.js

/** 
 * perim(Array<Array<Number>> ...list)
 *
 * takes in a set of points (in clockwise or counterclockwise order) and returns the perimeter of the polygon it forms
 * example call: `perim([-4, -2], [2, -5], [-4, -9]);`
**/
function perim(...list) {
    let total = 0;
    for (let index = 0; index < list.length; index++) {
        const point = list[index];
        let nextPoint = list[Number(index)+1];
        nextPoint ??= list[0];
        total += Math.sqrt((point[0]-nextPoint[0])**2 + (point[1]-nextPoint[1])**2);
    }
    return Math.round(total*100)/100;
}
perim([-4, -2], [2, -5], [-4, -9]); // 20.92