How do you calculate the average of an array in JavaScript?

Method 1: reduce (most common)

function average(arr) {
  if (arr.length === 0) return 0;
  const sum = arr.reduce((acc, val) => acc + val, 0);
  return sum / arr.length;
}

average([1, 2, 3, 4, 5]); // 3

Method 2: for loop

function average(arr) {
  if (arr.length === 0) return 0;
  let sum = 0;
  for (const num of arr) {
    sum += num;
  }
  return sum / arr.length;
}

One-liner

const avg = arr => arr.reduce((a, b) => a + b, 0) / arr.length;

avg([10, 20, 30]); // 20

Edge Cases to Handle

• Empty arrays must be handled to avoid dividing by 0 (which produces NaN)
• Non-numeric values in the array may cause NaN results

function safeAverage(arr) {
  const nums = arr.filter(n => typeof n === 'number' && !isNaN(n));
  if (nums.length === 0) return 0;
  return nums.reduce((a, b) => a + b, 0) / nums.length;
}