How to get text inside Old Compose window of Gmail with Javascript for Chrome extension

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Javascript

chrome

I am developing a chrome extension in which i need inner text of Gmail compose window ( Compose window will have some lines pre appended from my extension ) and its working fine with new compose window. But when i switch to Old compose window and select Plain text or RichText window i am not able to find the text inside compose window. Currently i am finding all "div" tags and one by one finding the index of pre appended text . But in old compose i am not able to find all "div" tags means i am not getting the div which contains my pre appended text. any one has idea how to fetch all "div" elements or text from gmail old gmail compose?

Thanks