javascript - Firefox extension: how to fill an input text field -

i have custom toolbar button created in accordance tutorial. javascript code button following:

custombutton = {  1: function () {   alert("just testing")    },  } 

and works. when click on button, alert happens. i'm trying make changes, namely, fill input field on clicking button, piece of code doesn't work:

custombutton = {  1: function () {   document.getelementbyid("loginusername").value = "aaaa";     },  } 

the element id "loginusername" exists on page. can fill selenium webdriver:

driver.findelement(by.id("loginusername")).sendkeys(user).  

so question why doesn't work in firefox extension?

thanks, racoon

your toolbar button , input field (assuming latter part of web page) live in separate documents. it's easy cross boundary. change code to

gbrowser.contentdocument.getelementbyid("loginusername").value = "aaaa";