JSON Patch

I imagine something like so:

   {
   "delete":["123-234","567-700"],

   "insert":[123,456],

   "substrs":[{"foo":"bar"},[]]
   }

Then delete the ranges from the string, convert the substrs to strings and insert them at the offset.

I'm not sure I understand what you mean, but it almost sounds like something we already have a single verb for: "splice". It means "replace this range with these values":

  z = ['a', 'b', 'c', 'd', 'e', 'f']
  z.splice(2, 3, 'w', 'x', 'y', 'z')

  Array(7) [ "a", "b", "w", "x", "y", "z", "f" ]

Unfortunately it's not on strings in javascript, but the verb has basically that meaning even outside of programming and could work here too.

I don't see how the values in your example would work though.