Set all vector elements to NA in a list of vectors

Question

How can I set all vector elements to NA in a list of vectors?

Essentially, I'd like to keep an existing list's structure and names but empty all values, to fill them in later. I provide a minimal example with a couple solutions below. I prefer base and tidyverse (esp. purrr) solutions, but can get on board with any approach which is better than what I have below.

my_list <- list(A = c('a' = 1, 'b' = 2, 'c' = 3), B = c('x' = 10, 'y' = 20))
ret_list <- my_list

# Approach 1
for (element_name in names(my_list)) {
  ret_list[[element_name]][] <- NA
}

ret_list
# $A
# a  b  c 
# NA NA NA 
# 
# $B
# x  y 
# NA NA 

# Approach 2    
lapply(my_list, function(x) {x[] <- NA; return(x)})
# $A
# a  b  c 
# NA NA NA 
# 
# $B
# x  y 
# NA NA 

Answer 1

Another way around

relist(replace( unlist(my_list), TRUE, NA ), skeleton = my_list)

#$A
# a  b  c 
#NA NA NA 

#$B
# x  y 
#NA NA