How do I extract even elements of an Array?

Question

var arr = [4, 5, 7, 8, 14, 45, 76];

function even(a) {
  var ar = [];

  for (var i = 0; i < a.length; i++) {
    ar.push(a[2 * i + 1]);
  }

  return ar;
}

ale         


        

Answer 1

Even if this question is quite old, I would like to add a one-liner filter:
Odd numbers: arr.filter((e,i)=>i%2)
Even numbers: arr.filter((e,i)=>i%2-1)
A more 'legal' way for even numbers: arr.filter((e,i)=>!(i%2))

There's no need to check with i%2===1 like sumit said; as mod 2 already returns a 0 or a 1 as numbers, they can be interpreted as boolean values in js.

Answer 2

You need to test the elements for evenness like this:

var arr = [4,5,7,8,14,45,76];

function even(a){
  var ar = [];

  for (var i=0; i<a.length;i++){
    if (a[i] % 2 === 0)
    {
      ar.push(a[i]);
    }

  }

return ar;
}

alert(even(arr));

%2 is the modulo operator, it returns the remainder of integer division.