First, get the text:
var text=$("#x").text();
Then split it:
var items=text.split(',');
If there's no items, you'll have an empty string as the only element of the array. If so, empty the array:
if(items.length==1&&items[0]=="") {
items=[];
}
Now convert everything to an integer: (note that this step isn't actually required, but if you're doing anything else with items, it's nice to have)
items=items.map(function(str) { return parseInt(str, 10); });
Put the item you want to remove in a variable:
var itemToRemove=3;
Find that in the array:
var index=items.indexOf(itemToRemove);
If it was found, splice it out of the array:
if(index!==-1) {
items.splice(index, 1);
}
Join the items back together:
text=items.join(',');
Put it back in the element:
$("#x").text(text);