function (input) {
    debug('optionalTextFilter(%s)', input);
    if (_.isString(input)) return input;
    if (_.isBoolean(input)) return (input ? '' : undefined);
    if (_.isNumber(input)) return '' + input;
    return undefined;
  }
function (input) {
    debug('optionalTextFilter(%s)', input);
    if (_.isString(input)) return input;
    if (_.isBoolean(input)) return (input ? '' : undefined);
    if (_.isNumber(input)) return '' + input;
    return undefined;
  }
function ( input ) { debug ( 'optionalTextFilter(%s)' , input ) ; if ( _ . isString ( input ) ) return input ; if ( _ . isBoolean ( input ) ) return ( input ? '' : undefined ) ; if ( _ . isNumber ( input ) ) return '' + input ; return undefined ; }
Given some text or the empty string return it.
If we receive true return empty string.
If we receive a number convert it to a string and return it.
Otherwise return undefined.

@param {(string|boolean|number|undefined|null)} input
@returns {(string|undefined)}
Given some text or the empty string return it . If we receive true return empty string . If we receive a number convert it to a string and return it . Otherwise return undefined .