src/config.js
function changeCfgOption(options, key) {
  if (expectKey(options, key, typeof cfg[key])) {
    cfg[key] = options[key]
  }
}
function changeCfgOption(options, key) {
  if (expectKey(options, key, typeof cfg[key])) {
    cfg[key] = options[key]
  }
}
function changeCfgOption ( options , key ) { if ( expectKey ( options , key , typeof cfg [ key ] ) ) { cfg [ key ] = options [ key ] } }
if supplied options contain given field, override its value in global cfg
if supplied options contain given field override its value in global cfg