Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <head> <script> function changeText() { var x=document.getElementById("mySelect"); x.options[x.selectedIndex].text="Melon"; } </script> </head> <body> <form> Select your favorite fruit: <select id="mySelect"> <option>Apple</option> <option>Orange</option> <option>Pineapple</option> <option>Banana</option> </select> <br><br> <input type="button" onclick="changeText()" value="Set text of selected option"> </form> </body> </html>
Result:
W3Schools.com - Try it yourself