for learning purposes I want to get every second element of an array. I succeeded with a for loop:

  const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

  function filterEverySecond(arr) {
    let everySecondEl = [];
    for (let i = 0; i < arr.length; i  = 2) {
      everySecondEl.push(arr[i]);
    }
    return everySecondEl;
  }

  console.log({
    numbers,
    result: filterEverySecond(numbers)
  });

Now I want to achieve the same without a for loop, but by using array methods (forEach, filter, map or reduce). Can anyone recommend which method would be best here?

CodePudding user response：

you can do it easily with filter

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

const filtered = numbers.filter((_, i) => i % 2 === 0)

console.log(filtered)

you just filter out the elements that have a odd index

CodePudding user response：

You can use filter and check if the index of the current array element is divisible by 2:

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

console.log({
  numbers,
  result: numbers.filter((_, index) => index % 2 === 0)
});

CodePudding user response：

You can use filter for index.

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
console.log({
    numbers,
    result: numbers.filter((n,i)=>i%2==0)
});

CodePudding user response：

You could use a for each loop like so to get the same desired output:

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const result = [];

numbers.forEach(number => {
    if (number % 2 != 0) {
        result.push(number);
    }
});

console.log(numbers);
console.log(result);

The modulus operator returns the remainder of the two numbers when divided. For example: 1 % 2 will return 1 as the remainder. So in the if statement we are checking if the number is not divisible by 2.