ymPrompt's doHandler method to implement the method of obtaining the return value of the child window_javascript skills

I was very depressed and still didn’t give up. I read the introduced method from beginning to end. When I saw doHandler, there were two parameters sign and autoClose. After reading the method introduction, I felt that this method was feasible (I had always used it before). ymPrompt.close method to directly close the child window), I wrote a script to test it, and it can achieve what I want. I will post the code as follows:
Parent window code: