Question

how to make the first option selected? I tried this but doesnt work:

  selectElement.options[0].selected=true;

it gives me this error:

   Uncaught TypeError: Cannot read property '0' of undefined

update

solved! by defining selectElement correctly.

Answer 1

Try this (See the demo)

HTML

<select id="selectElement">
    <option>First</option>
    <option selected>Second</option>
</select>

JavaScript

selectElement.options[0].selected="selected";

Or you can do selectElement.options[0].selected=true;

Hope this works for you.