How to make a radiobutton which can write something if i click it?

Question

for example,

vehicle:
¤ car
¤ motorcycle
¤ bus
¤ other, _________

so i can fill in the blank if i choose "other"

Answer 1

Give the radio button an id, and the when clicked:

if (document.getElementById("rbtn").checked){
document.getElementById("other-text").style.display = visible; }

or you could use jQuery to toggle classes, but in theory just hide and show the target element. What you'll make visible is the text area.