修复代码时持续遇到「Expected an assignment or function call...」错误求助

这个错误是因为代码检查工具（比如ESLint）禁止将三元运算符作为独立语句使用。三元运算符本质是表达式，它的结果需要被赋值、传递或使用，而你这里用它来执行条件赋值，false分支返回的null没有被处理，属于无意义的表达式语句，触发了规则校验。

另外注意你的代码里有两处小问题：函数名拼写错误constrcutFilterOptions（少了个u），以及常量TIMEFILTERUNIT末尾缺失分号，这些也建议一并修正。

下面是几种可行的修复方案：

方案一：替换为if语句（最直观易读） #

const CHARTID = "chart_id";
const FIELDID = "field_id";
const TIMEFILTERVALUE= "time_filter_input";
const TIMEFILTERUNIT = "time_filter_type";
const UNITFILTER = "unit_filter";

const constructFilterOptions = (field_id, chartId, timeFilterType, timeFilterUnit, unit)=> {
  var filterObj = {};
  if (!_.isNil(field_id)) filterObj[FIELDID] = field_id;
  if (!_.isNil(chartId)) filterObj[CHARTID] = chartId;
  if (!_.isNil(timeFilterType)) filterObj[TIMEFILTERUNIT] = timeFilterType;
  if (!_.isNil(timeFilterUnit)) filterObj[TIMEFILTERVALUE] = timeFilterUnit;
  if (!_.isNil(unit)) filterObj[UNITFILTER] = unit;

  return filterObj;
}

方案二：ES6+对象字面量条件属性（更简洁） #

利用展开运算符，仅当值非空时向对象添加对应属性：

const CHARTID = "chart_id";
const FIELDID = "field_id";
const TIMEFILTERVALUE= "time_filter_input";
const TIMEFILTERUNIT = "time_filter_type";
const UNITFILTER = "unit_filter";

const constructFilterOptions = (field_id, chartId, timeFilterType, timeFilterUnit, unit)=> {
  return {
    ...(!_.isNil(field_id) && { [FIELDID]: field_id }),
    ...(!_.isNil(chartId) && { [CHARTID]: chartId }),
    ...(!_.isNil(timeFilterType) && { [TIMEFILTERUNIT]: timeFilterType }),
    ...(!_.isNil(timeFilterUnit) && { [TIMEFILTERVALUE]: timeFilterUnit }),
    ...(!_.isNil(unit) && { [UNITFILTER]: unit })
  };
}

方案三：强制使用三元运算符（不推荐，冗余） #

如果一定要保留三元写法，需要将表达式结果赋值给变量（虽然完全没必要，但能通过检查）：

const CHARTID = "chart_id";
const FIELDID = "field_id";
const TIMEFILTERVALUE= "time_filter_input";
const TIMEFILTERUNIT = "time_filter_type";
const UNITFILTER = "unit_filter";

const constructFilterOptions = (field_id, chartId, timeFilterType, timeFilterUnit, unit)=> {
  var filterObj = {};
  let temp;
  temp = !_.isNil(field_id) ? filterObj[FIELDID] = field_id : null;
  temp = !_.isNil(chartId) ? filterObj[CHARTID] = chartId : null;
  temp = !_.isNil(timeFilterType) ? filterObj[TIMEFILTERUNIT] = timeFilterType : null;
  temp = !_.isNil(timeFilterUnit) ? filterObj[TIMEFILTERVALUE] = timeFilterUnit : null;
  temp = !_.isNil(unit) ? filterObj[UNITFILTER] = unit : null;

  return filterObj;
}

内容的提问来源于stack exchange，提问作者Suraya Zulkifli