What are Keycodes?
I've adopted Vim (Neovim and other Vim editor plugins for VS Code and JetBrains) within the past year and the most challenging aspect was learning all of the different keymaps and motions. I will say that I am still learning but have become pretty efficient with the foundational keymaps and motions in Vim. In my opinion, one of Vim's greatest strengths is the robust documentation and manual pages. If you want to learn to do something in Vim, I guarantee it is documented somewhere in the help documentation. I'm not going to say the information is always easy to find, but it is available if you're patient enough to search.
The power of Vim comes from the keyboard. The navigation and editing experience in Vim is different from almost all modern editors in that it prefers the use of the keyboard over the mouse. This difference in style can lead to a pretty steep learning curve and frustration. For me, the frustration early on came from not being able to understand the different keycodes listed in the documentation. For example, when the documentation for performing a specific action references the <Leader> or <C-j> key, what exactly does this mean? Understanding what these keycodes mean, will allow us to gain more knowledge from the Vim documentation.
Keycode Reference
In this section, we're going to go through several keycodes that aren't immediately obvious (at least to me). Some of the keycodes are pretty self-explanatory, like <Esc> represents the escape key and <Space> represents the space bar. In the examples, you may see characters followed by ..., which means that the keycode can be combined with other keys to perform a specific action. For example, we might see something like <Space>-... which means that the combination of the space bar and some undetermined subsequent key(s) will define the action.
: The leader key isn't exactly a keycode, but it is often referred to in documentation and provides a lot of flexibility for creating very custom keymap shortcuts. - By defaut, the leader key is mapped to
\
- By defaut, the leader key is mapped to
<CR>,<Enter>,<Return>: The enter key (CRstands for carriage return)<S-...>: The shift key<C-...>: The control key<M-...>,<A-...>: The meta or alt key. On Windows, this is alt and on macOS this is option.<D-...>: The command key (macOS only)
This list may seem small and pretty meaningless, but I can assure you that you will come across these keycodes in Vim and Vim plugin documentation. The power of Vim lies in the use of keymaps and shortcuts, so if you can master the fundamentals and understand how to learn from the documentation Vim will be a joy to use.
In the next section, we'll take a look at some examples of these keycodes as they are used with certain keymaps and plugins. Since I use Neovim, I'll be providing examples in both Vimscript and Lua. If you're not familiar with Lua, it is a great scripting language and also the default plugin language for Neovim. Neovim still supports Vimscript, but I've seen more and more plugins created using Lua lately.
Keycode Examples
The examples below will be focused mainly on how to interact with Neovim configuration. While Neovim is essentially backward compatible with Vim, there may be some differences. To test these examples out they can be placed in your init.lua, init.vim, or another configuration file if your environment is set up differently.
Setting the Leader key
As I mentioned previously the leader key is defaulted to \, but it is common for people to want to change it to a different character. In the examples below we are going to map the leader key to the comma key. This means that any keymapping that involves the <Leader> keycode will involve the use of the comma key instead of the default backslash.
" Vimscript
let mapleader = ","
-- Lua
vim.g.mapleader = ','
Using the NERDTree plugin as an example. If we wanted to invoke the :NERDTreeFocus command, with a keymap that involves our newly mapped leader key that would look something like this.
" Vimscript
nnoremap <leader>n :NERDTreeFocus<CR>
-- Lua
vim.api.nvim_set_keymap('n', '<leader>n', ':NERDTreeFocus<CR>, { noremap = true, silent = true })
Both of the above commands will result in a keymap the invokes :NERDTreeFocus when the combination of the , + n is pressed. If you'd like to learn a bit more about the Lua function used here to set the keymap, check out the documentation here.
At this point, you should have a pretty good idea of the fundamentals of Vim keycodes and how to apply them when reading the help documentation.