code: function buildConfig( wantedEnv )
  {
  
      const isValid = wantedEnv &&
          wantedEnv.length > 0 && allowedEnvs.indexOf( wantedEnv ) !== -1;
      const validEnv = isValid ? wantedEnv : 'dev';
  
      return configs[ validEnv ];
  }
docs: Build the webpack configuration
  @param  {String} wantedEnv The wanted environment
  @return {Object} Webpack config