Check variables and add them to comma separated list

Question

I have 4 javascript variables:

a = 'first';
b = 'second';
c = 'third';
d = 'fourth';

What i want to achieve is to get them separated by comma, BUT. Sometimes where could be situations that some variables could be empty. Here is some of examples:

EXAMPLE1:

a = 'first';
b = '';
c = 'third';
d = '';

OUTPUT should be: first, third

EXAMPLE2:

a = '';
b = 'second';
c = '';
d = 'fourth';

OUTPUT should be: second, fourth

Maybe someone could help me to solve this?

Answer 1

Use .filter() as shown :-

a = '';
b = 'second';
c = '';
d = 'fourth';

var arr=[];
arr.push(a)
arr.push(b)
arr.push(c)
arr.push(d)
var newarr = arr.filter(function(value){
  return $.trim(value) != '' && value != null;
});
newarr = newarr.join(',');
alert(newarr);

Working Demo

Answer 2

The simpler solution (but not necessarily the more efficient) is :

var arr = [];
if (a) 
  arr.push(a);

if (b) 
  arr.push(b);

if (c) 
  arr.push(c);

if (d) 
  arr.push(d);

var commaSeparated = arr.join(',');

I like using an array for this kind of problem because you don't have to worry about append or not the commas to your result string.