stylelint-bundle-worker.js
function collapse(str, ch) {
  var res = str.split(ch);
  var isFirst = res[0] === '';
  var isLast = res[res.length - 1] === '';
  res = res.filter(Boolean);
  if (isFirst) res.unshift('');
  if (isLast) res.push('');
  return res.join(ch);
}
function collapse(str, ch) {
  var res = str.split(ch);
  var isFirst = res[0] === '';
  var isLast = res[res.length - 1] === '';
  res = res.filter(Boolean);
  if (isFirst) res.unshift('');
  if (isLast) res.push('');
  return res.join(ch);
}
Collapse repeated character sequences.

```js
collapse('a/../../../b', '../');
//=> 'a/../b'
```

@param  {String} `str`
@param  {String} `ch` Character sequence to collapse
@return {String}