Sum of Array Elements - JavaScript Program

// Method 1: Using for loop function sumArray(arr) { let sum = 0; for (let i = 0; i < arr.length; i++) { sum += arr[i]; } return sum; } let numbers = [1, 2, 3, 4, 5]; console.log("Array:", numbers); console.log("Sum:", sumArray(numbers)); // Method 2: Using reduce function sumArrayReduce(arr) { return arr.reduce((acc, num) => acc + num, 0); } console.log("\nUsing reduce:", sumArrayReduce([10, 20, 30])); // Method 3: Using forEach function sumArrayForEach(arr) { let sum = 0; arr.forEach(num => sum += num); return sum; } console.log("\nUsing forEach:", sumArrayForEach([5, 10, 15])); // Method 4: Using for...of loop function sumArrayForOf(arr) { let sum = 0; for (let num of arr) { sum += num; } return sum; } console.log("\nUsing for...of:", sumArrayForOf([2, 4, 6, 8])); // Method 5: One-liner const sum = arr => arr.reduce((a, b) => a + b, 0); console.log("\nOne-liner:", sum([1, 2, 3, 4, 5])); // Method 6: Sum with condition (even numbers only) function sumEvenNumbers(arr) { return arr.filter(num => num % 2 === 0) .reduce((acc, num) => acc + num, 0); } console.log("\nSum of even numbers:", sumEvenNumbers([1, 2, 3, 4, 5, 6]));

This program demonstrates different methods to sum array elements.

Method 1: For Loop

Traditional approach:

javascript
let sum = 0;
for (let i = 0; i < arr.length; i++) {
    sum += arr[i];
}

Method 2: Reduce

Most common modern approach:

javascript
arr.reduce((acc, num) => acc + num, 0);

Initial Value:

0 is the starting accumulator value
Important for empty arrays

Method 3: ForEach

Functional iteration:

javascript
let sum = 0;
arr.forEach(num => sum += num);

Method 4: For...Of Loop

ES6 iteration:

javascript
for (let num of arr) {
    sum += num;
}

For...Of vs For Loop:

For...of: Cleaner, works with any iterable
For loop: More control, index access

Method 5: Arrow Function

One-liner:

javascript
const sum = arr => arr.reduce((a, b) => a + b, 0);

Method 6: Conditional Sum

Sum only even numbers:

javascript
arr.filter(num => num % 2 === 0)
   .reduce((acc, num) => acc + num, 0);

Chaining Methods:

filter(): Creates new array with matching elements
reduce(): Sums filtered array

Performance:

All methods: O(n) time complexity
Reduce: Slightly more efficient (single pass)

When to Use:

Reduce: Most common, functional
For loop: Learning, custom logic
For...of: Clean iteration
One-liner: Quick calculations

Output