Append number to a comma separated list

the list looks like:

3434,346,1,6,46

How can I append a number to it with javascript, but only if it doesn't already exist in it?

---

Assuming your initial value is a string (you didn't say).

var listOfNumbers = '3434,346,1,6,46', add = 34332;
var numbers = listOfNumbers.split(',');
if(numbers.indexOf(add)!=-1) {
  numbers.push(add);
}
listOfNumbers = numbers.join(',');

Basically i convert the string into an array, check the existence of the value using indexOf(), adding only if it doesn't exist.

I then convert the value back to a string using join.

---

If that is a string, you can use the .split() and .join() functions, as well as .push() :

var data = '3434,346,1,6,46';
var arr = data.split(',');

var add = newInt;
arr.push(newInt);
data = arr.join(',');

If that is already an array, you can just use .push() :

var data = [3434,346,1,6,46];
var add = newInt;

data.push(add);

UPDATE: Didn't read the last line to check for duplicates, the best approach I can think of is a loop:

var data = [3434,346,1,6,46];
var add = newInt;

var exists = false;
for (var i = 0; i < input.length; i++) {
    if (data[i] == add) {
        exists = true;
        break;
    }
}

if (!exists) {
    data.push(add);

    // then you would join if you wanted a string
}

---

You can also use a regular expression:

function appendConditional(s, n) {
  var re = new RegExp('(^|b)' + n + '(b|$)');
  if (!re.test(s)) {
    return s + (s.length? ',' : '') + n;
  }
  return s;
}

var nums = '3434,346,1,6,46'

alert( appendConditional(nums, '12') ); // '3434,346,1,6,46,12'
alert( appendConditional(nums, '6') );  // '3434,346,1,6,46'

Oh, since some really like ternary operators and obfustically short code:

function appendConditional(s, n) {
  var re = new RegExp('(^|b)' + n + '(b|$)');
  return s + (re.test(s)? '' : (''+s? ',':'') + n );
}

No jQuery, "shims" or cross-browser issues. :-)

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