how to write a nested if else statement in data.table r

Below is a general form of nested if-else statement using dplyr package. So I have two questions

• What is the equivalent code using data.table the below form?
• is there any other faster function to be replaced to str_detect() to speed up the below code?

# assuming we have two data frames x and y ;
x <- mutate(x, test =ifelse(x$A %in% y$A & x$B %in% y$C, "Number 1",
                     ifelse(str_detect(x$D,"TB"),        "exclude",                                                                            
                     ifelse(str_detect(x$D,"GL"),        "exclude",
                     ifelse(x$E %in% y$`B`,              "exclude", test))))))

my real code has 10 more ifesle in the above code line.