electron - i can't change css in iframe but run in console.log It works

Question

i want to change bgcolor of mainHeader and sidebar

this code work in console.log but not work in javascript function

iframe.contentWindow.document.getElementsByClassName('MainHeader jsx-1834506763')[0].style.backgroundColor = data

question from:https://stackoverflow.com/questions/65880226/i-cant-change-css-in-iframe-but-run-in-console-log-it-works

Answer 1

Waitting for answers