Function operation

static/editor.md/lib/codemirror/lib/codemirror.js:3071–3078

(cm, f)

  }
  // Wraps a function in an operation. Returns the wrapped function.
  function operation(cm, f) {
    return function() {
      if (cm.curOp) return f.apply(cm, arguments);
      startOperation(cm);
      try { return f.apply(cm, arguments); }
      finally { endOperation(cm); }
    };
  }
  // Used to add methods to editor and doc instances, wrapping them in
  // operations.
  function methodOp(f) {