switchCase.js

/* jshint esversion: 6 */

function swichCase ( str ) {
  chars = str.split( '' );

  for ( let i = 0; i < chars.length; i++ ) {
    if ( ( chars[ i ].charCodeAt() > 64 && chars[ i ].charCodeAt() < 91 ) || ( chars[ i ].charCodeAt() > 191 && chars[ i ].charCodeAt() < 224 ) ) {
      chars[ i ] = String.fromCharCode( chars[ i ].charCodeAt() + 32 );
    }
    else if ( ( chars[ i ].charCodeAt() > 96 && chars[ i ].charCodeAt() < 123 ) || ( chars[ i ].charCodeAt() > 223 && chars[ i ].charCodeAt() < 256 ) ) {
      chars[ i ] = String.fromCharCode( chars[ i ].charCodeAt() - 32 );
    }
  }
  return 'orig: ' + str + ' mod: ' + chars.join( '' );
}

console.log( swichCase( "aA" ) );
console.log( swichCase( "aSfrt5JHkj(p" ) );