如何提取数组中的元素?

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;
}

alert(even(arr));
var arr = [4, 5, 7, 8, 14, 45, 76];

function e