There are multiple ways to get the sum of numbers in even positions in an array. Let us look at 3 of these −
Using a for loop
We can directly use a for loop and get the sum.
Example
let arr = [1, 2, 3, 4, 5, 6]; let sum = 0; for(let i = 0; i < arr.length; i += 2) { sum += arr[i]; } console.log(sum);
Output
9
Using a forEach loop
In this method, instead of iterating explicitly over the array, we can instead use the built in function forEach to iterate. It takes a function that is executed for each element.
Example
let arr = [1, 2, 3, 4, 5, 6]; let sum = 0; arr.forEach((elem, i) => { if(i % 2 === 0) { sum += elem; } }); console.log(sum);
Output
9
Using filter and reduce
We can use filter and reduce functions to calculate the sum. First we filter the odd indices using filter then we calculate the sum using reduce.
Example
let arr = [1, 2, 3, 4, 5, 6]; let sum = arr.filter((_, i) => i % 2 === 0).reduce((curr, acc) => acc + curr, 0) console.log(sum);
Output
9