function expand_r(options, lines, prefix) {
  Object.getOwnPropertyNames(options).forEach(function(key) {
    var full = prefix.concat(key);
    var value = options[key];

    if (Array.isArray(value)) {
      value.forEach(function(val) {
        lines.push(full.concat(val).join(' '));
      });      
    }
    else if (typeof(value) == 'object') {
      expand_r(value, lines, full);
    }
    else {
      lines.push(full.concat(value).join(' '));
    }
  });
}
function expand_r(options, lines, prefix) {
  Object.getOwnPropertyNames(options).forEach(function(key) {
    var full = prefix.concat(key);
    var value = options[key];

    if (Array.isArray(value)) {
      value.forEach(function(val) {
        lines.push(full.concat(val).join(' '));
      });      
    }
    else if (typeof(value) == 'object') {
      expand_r(value, lines, full);
    }
    else {
      lines.push(full.concat(value).join(' '));
    }
  });
}
function expand_r ( options , lines , prefix ) { Object . getOwnPropertyNames ( options ) . forEach ( function ( key ) { var full = prefix . concat ( key ) ; var value = options [ key ] ; if ( Array . isArray ( value ) ) { value . forEach ( function ( val ) { lines . push ( full . concat ( val ) . join ( ' ' ) ) ; } ) ; } else if ( typeof ( value ) == 'object' ) { expand_r ( value , lines , full ) ; } else { lines . push ( full . concat ( value ) . join ( ' ' ) ) ; } } ) ; }
Recursively expand `options` into `lines` with a `prefix`.

@private
@static
@category udhcpd
@param {object} options The dhcp server configuration.
@param {array} lines The lines of the configuration file.
@param {array) prefix The key prefix.
Recursively expand options into lines with a prefix .