const myMongooseQuery =  {$regex: this._diacriticSensitiveRegex(valueMatch), '$options' : 'i'};

​

# having this function defined in you code

  // credit : https://stackoverflow.com/questions/36647244/mongodb-how-to-find-documents-ignoring-case-sensitive-accents-and-percent-like

  _diacriticSensitiveRegex(string = '') {

         return string

            .replace(/a/g, '[a,á,à,ä,â]')

            .replace(/A/g, '[A,a,á,à,ä,â]')

            .replace(/e/g, '[e,é,ë,è]')

            .replace(/E/g, '[E,e,é,ë,è]')

            .replace(/i/g, '[i,í,ï,ì]')

            .replace(/I/g, '[I,i,í,ï,ì]')

            .replace(/o/g, '[o,ó,ö,ò]')

            .replace(/O/g, '[O,o,ó,ö,ò]')

            .replace(/u/g, '[u,ü,ú,ù]')

            .replace(/U/g, '[U,u,ü,ú,ù]');

  }

(?i) case-insensitive mode ON    

(?-i) case-insensitive mode OFF

​

​

Modern regex flavors allow you to apply modifiers to only part of the regular expression. 

If you insert the modifier (?im) in the middle of the regex then the modifier only applies 

to the part of the regex to the right of the modifier. With these flavors, you can turn off 

modes by preceding them with a minus sign (?-i).