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; }  alert(even(arr)); 

http://jsbin.com/unocar/2/edit

I have tried this code in order to output even (index) elements of an array. It works, but it also outputs some empty elements. How do I fix this code to output only existing elements?

Answer 1

Either use modulus:

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

or skip every second element by incrementing i accordingly:

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

Notice: Your code actually takes the elements with odd indexes from the array. If this is what you want you have to use i % 2 === 1 or start the loop with var i = 1 respectively.