I should have set a timer on this one but I think it took 10 mins. This is what I ended up with in javascript - notice that it can print the whole triangle as a by-product of the implementation, but also because I have a (bad) habit of doing more than just what was required. Most of the implementation (testing) issues I suffered were due to lack of js knowledge (where is clone?) but the original skeleton of code that I wrote just thinking about the problem didn't need to change. I wouldn't have got it exactly right without a debugger though.

   function printPascal(x, triangle) {
      var row = [];
      while (x) {
         var next = clone(row);
         next.push(1);
         for (var i = 0; i < row.length - 1; i++)
            next[i + 1] = row[i] + row[i + 1];
         row = next;
         x--;
         if (triangle)
            print(whitespace(x) + row);
      }
      if (!triangle)
         print(row);
   }

   function clone(list) {
      var clone = [];
      for (i in list)
         clone.push(list[i]);
      return clone;
   }

   function whitespace(x) {
      var white = " ";
      while (x) {
         white += " ";
         x--;
      }
      return white;
   }

   printPascal(10);

Ignoring the whitespace and clone functions, is there a much simpler way of doing this?