Function option

static/editor.md/lib/codemirror/lib/codemirror.js:5162–5166

(name, deflt, handle, notOnInit)

  var optionHandlers = CodeMirror.optionHandlers = {};

  function option(name, deflt, handle, notOnInit) {
    CodeMirror.defaults[name] = deflt;
    if (handle) optionHandlers[name] =
      notOnInit ? function(cm, val, old) {if (old != Init) handle(cm, val, old);} : handle;
  }

  // Passed to option handlers when there is no old value.
  var Init = CodeMirror.Init = {toString: function(){return "CodeMirror.Init";}};