How can I toggle between single and multi-line expressions of arrays?

Question

This is probably easier to explain with an example. I prefer expressing things like

const array = { a: 1, b: 2, c: 3 }

on a single line at first but eventually I might want to switch to

const array = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
}

as the array gets longer. I realized that I'm not doing this very efficiently and I was wondering if there's some builtin way, or at least a more elegant way, to toggle between the two different styles.

Answer 1

There's a plugin called SplitJoin.vim that aims to address exactly your problem. Find it here: https://github.com/AndrewRadev/splitjoin.vim

Answer 2

I think @nobe4's solution is more elegant, but I already wrote this :). So here's something I whipped up:

nnoremap <key> :call ToggleArrayFormat()<CR>

function! ToggleArrayFormat()
   let direction = search('}', 'cnp', line('.'))
   if (direction)
      normal! 0f{a^M
      while (search(',', 'cnp', line('.')))
         normal! f,a^M
      endwhile
      normal! f}i^M
   else
      echom "stuff"
      while !search('}', 'cnp', line('.'))
         normal! J
      endwhile
   endif
endfunction

• ^M is not a literal "^M" and needs to be retyped with Ctrl+v, Enter (All three).
• Replace <key> with whaveter key sequence you want.
• Place your cursor anywhere on the first line of the array and press <key> to toggle the formatting

See :h search() and :h normal for more info.

Hope it helps.

Answer 3

Here is a slight workaround, which is interesting to learn new functionalities and can solve your problem:

If you consider having a , after each element in your array (which is valid, given the 2nd expression), you can use a substitution to do the job:

:s/\({\|,\)/\1\r/g

Let's break it down:

:s/                    create a substitution command
\(                     create a matching group for your regex
{\|,                   match a { OR a ,
\)                     end the matching group
/                      substitute the matched regex with 
\1                     the element matched in the group: a { or a ,
\r                     a end of line character
/g                     apply for all matching of the line

So you'll get:

const array = {
  a: 1,
  b: 2,
  c: 3,
  }

With your cursor on the last {, and from there << will de-indent the closing curly brace.

---

Now if you want to do the other way around, select your array in linewise Visual mode and simply press J.

This will Join the lines into one.

Or (as VanLaser) suggested, on the first or last line you can do:

V%J

• V will enter linewise visual mode
• % will go to the matching curly brace
• J will join the lines

---

Some reading:

• :h \|
• :h \(
• :h \1
• :h v_J
• :h %