Putting optional arguments after a callback hurts readability of the code: `callback` should always be the last named parameter: `( blob, [ limit, [ callback ]] )`:

```js
getResizedImgBlob: function ut_getResizedImgBlob(blob, limit, callback) {
  // ... normalize the arguments in the implementation..
  if ( typeof limit === 'function' ) {
    callback = limit;
    limit = 300 * 1024;
  }
  ...
```