Convert operations(operator, motion, text-object) to JS

[t9md]

To let me understand how it is, clarify requirement.

TODO( 🚢 released)

• Eliminate 2nd param of Base constructor and if necessary, modify props after construction.
• Update example code in Wiki
• Find the way to notify user to inform extending JS class by coffee is no longer supported. I don't thins there is it.
  • Refs: Extending an ES6 class with a CS class fails jashkenas/coffeescript#4233
• Convert coffee based vmp-plugin to JS.
  • vmp-ex-mode Decaffeinate atom-vim-mode-plus-ex-mode#27 🚢
  • vmp-jasmine-increase-focus convert complete, and fix spec to adapt to atom-core's asyncSave atom-vim-mode-plus-jasmine-increase-focus#4 🚢
  • vmp-move-to-symbols decaffeinate atom-vim-mode-plus-move-to-symbols#2 🚢
  • vmp-move-selected-text decaffeinate atom-vim-mode-plus-move-selected-text#6 🚢
  • vmp-replace-with-execution decaffeinate atom-vim-mode-plus-replace-with-execution#1 🚢
  • vmp-plugin-sample translate to JavaScript and fix broken link atom-vim-mode-plus-plugin-sample#1 🚢
  • quick-highlight remove use of babel(change mind) atom-quick-highlight#24 🚢
  • vim-mode-plus-exchange Decaffeinate for upcoming vmp-core change dillonkearns/atom-vim-mode-plus-exchange#3
  • vim-mode-plus-duplicate Decaffeinate for upcoming vmp-core change dillonkearns/atom-vim-mode-plus-duplicate#1
  • artarf/git-diff-staged [change require] vim-mode-plus operation class need defined by ES6. artarf/git-diff-staged#1

Migration best practices memo

• Basic rule is to move logic to from constructor or initialize to execute().
• In ES6 class's constructor, super must be called first to refer this.
• So we no longer do following logic.
  • Old way in CoffeeScript
    1. set this.prop
    2. then call super
    3. In parent's constructor behave differently based on this.prop
  • New way in ES6
    1. always call super first in constructor
    2. set this.prop
    3. in execute, behave differently based on this.prop

Working memo

before conversion

had 2 layer

• klass.prototype.ivar
• instance.ivar

after conversion

only 1 layer (no prototype.ivar layer)

• instance.ivar

Caution

• ES6 class is not extendable by CS's class.
• Thus, converting breaks user's custom class in their init.coffee(if exists) or vmp-plugin package written in coffee.
• CS's executable class body is no longer availale.
• Class prop is not set on prototype, and it's set after constructor's super call.
• So don't expect these class props are available in parent's constructor.
  • Basically keep constructor function small and simple.
• In CS, Object.assign(this, prop) in constructor can overwrite properties defined in prototype, but in JS, properties are set after construction, so this approach must be replaced with new one.
  • I experimentally introduce Base.assign as replacement for constructor's 2nd arg(was prop directly Object.assign-ed in constructor.

[t9md]

Will merge. I won't go back anyway.
I like JS now over CoffeeScript basically because of prittier.