console.log(Object.keys(params).filter(key => params[key]).reduce((p, key) =>  p.append(key, params[key]),              new HttpParams())); //workconsole.log(Object.keys(params).filter(key => params[key]).reduce((p, key) => {p.append(key, params[key]); return p; }, new HttpParams())); //not work第一行返回值控制臺(tái)輸出正常。第二行返回值控制臺(tái)輸出時(shí)沒(méi)有寫(xiě)入?yún)?shù)。HttpParams {updates: Array(2), cloneFrom: HttpParams, encoder: HttpUrlEncodingCodec, map: null}HttpParams {updates: null, cloneFrom: null, encoder: HttpUrlEncodingCodec, map: null}