# library(xml2)
xml <- xml2::read_html("quux.xml") |> xml2::as_list()

## either data.table or dplyr ...
out <- dplyr::bind_rows(xml$html$body)
out <- data.table::rbindlist(xml$html$body, use.names = TRUE, fill = TRUE)

out
# # A tibble: 3 × 5
#   myname    myh       myfname   mylname   favcolor 
#   <list>    <list>    <list>    <list>    <list>   
# 1 <chr [1]> <NULL>    <NULL>    <NULL>    <NULL>   
# 2 <NULL>    <chr [1]> <chr [1]> <chr [1]> <NULL>   
# 3 <NULL>    <chr [1]> <chr [1]> <chr [1]> <chr [1]>

由于xml的结构，所有的列都是列表列，因为我们习惯于所有元素的长度都是0或1，所以我们可以迭代所有元素来提取第一个：

out[] <- lapply(out, function(z) sapply(z, function(y) if (is.null(y)) NA else unlist(y)[1]))
out
# # A tibble: 3 × 5
#   myname myh   myfname mylname favcolor
#   <chr>  <chr> <chr>   <chr>   <chr>   
# 1 omi    NA    NA      NA      NA      
# 2 NA     59    Tom     John    NA      
# 3 NA     60    Alex    Tom     grey

数据：文件quux.xml，内容：

<HelloWorld created="2022-03-22" id="12we">
  <myname>omi</myname>
</HelloWorld>
<HelloWorld created="2022-03-12" id="18we">
  <myh>59</myh>
  <myfname>Tom</myfname>
  <mylname>John</mylname>
</HelloWorld>
<HelloWorld created="2022-03-30" id="188yye">
  <myh>60</myh>
  <favcolor>grey</favcolor>
  <myfname>Alex</myfname>
  <mylname>Tom</mylname>
</HelloWorld>