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));

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

for(var i = 0; i < a.length; i += 2) {  // take every second element
    ar.push(a[i]);
}

var arr = [4,5,7,8,14,45,76];
var filtered = arr.filter(function(element, index, array) {
  return (index % 2 === 0);
});

if (!Array.prototype.filter)
{
  Array.prototype.filter = function(fun /*, thisp */)
  {
    "use strict";

    if (this === void 0 || this === null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun !== "function")
      throw new TypeError();

    var res = [];
    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in t)
      {
        var val = t[i]; // in case fun mutates this
        if (fun.call(thisp, val, i, t))
          res.push(val);
      }
    }

    return res;
  };
}

[1,2,3,4,5].filter(function(num){ if( num % 2 ) return num;})

if ((i % 2) === 0) {
    ar.push(a[i])
}

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));

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

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

  for (x in a)
  {

    if((a[x]%2)==0)
    ar.push(a[x]);

  }
return ar;
}

alert(even(arr));