javascript - Ignore if-else ladder and implements strategic design pattern -

i trying implement strategic design pattern .

i have simple if-else ladder below:

       if(datakeyinresponse === 'year') {            bsd = new date(moment(new date(item['key'])).startof('year').format('yyyy-mm-dd'))            nestedbed = new date(moment(new date(item['key'])).endof('year').format('yyyy-mm-dd'));         } else if(datakeyinresponse === 'quarter') {             let tempdate = new date(moment(new date(item['key'])).add(2, 'months').format('yyyy-mm-dd'));             // nestedbed = new date(moment(new date(item['key'])).add(3, 'months').format('yyyy-mm-dd'));             nestedbed = new date(moment(tempdate).endof('month').format('yyyy-mm-dd'));         } else if(datakeyinresponse === 'month') {             nestedbed = new date(moment(new date(item['key'])).endof('month').format('yyyy-mm-dd'));         } else if(datakeyinresponse === 'week') {             //relying more on es start date week             nestedbed = new date(moment(new date(item['key'])).weekday(7).format('yyyy-mm-dd'));          } else {           // bed = bucketstartdate;           nestedbed = new date(item['key']);         } 

and implemented strategic pattern upon it:

interface emptybucketinterface {     fngetemptybuckets(); } class year implements emptybucketinterface {     fngetemptybuckets() {         bsd = new date(moment(new date(item['key'])).startof('year').format('yyyy-mm-dd'))         nestedbed = new date(moment(new date(item['key'])).endof('year').format('yyyy-mm-dd'));         return {             "bsd": bsd,             "nestedbed": nestedbed         };     } } class quarter implements emptybucketinterface {     fngetemptybuckets() {         let tempdate = new date(moment(new date(item['key'])).add(2, 'months').format('yyyy-mm-dd'));         nestedbed = new date(moment(tempdate).endof('month').format('yyyy-mm-dd'));         return {             "tempdate": tempdate,             "nestedbed": nestedbed         };     } } class month implements emptybucketinterface {     fngetemptybuckets() {         nestedbed = new date(moment(new date(item['key'])).endof('month').format('yyyy-mm-dd'));         return {             "nestedbed": nestedbed         };     } } class week implements emptybucketinterface {     fngetemptybuckets() {         nestedbed = new date(moment(new date(item['key'])).weekday(7).format('yyyy-mm-dd'));         return {             "nestedbed": nestedbed         };     } } 

but confused how invoke particular class based on condition

like in above if-else ladder checks datakeyinresponse value , execute statements

but here in strategic pattern how see condition , execute class.

any appreciated.

a simple example of strategy pattern:

public class someclass {     private final map<string, emptybucketinterface> strategies = new hashmap<string, emptybucketinterface>();      public someclass() {         strategies.put("year", new year());         strategies.put("quarter", new quarter());         strategies.put("month", new month());         strategies.put("week", new week());     }      public void doaction(string action) {         strategies.get(action).fngetemptybuckets();     } } 

you may take @ this: https://www.tomasmalmsten.com/2011/01/create-factory-strategies-ifs/ encapsulate strategies creation in factory.

advice: should name classes capitalized first-letter emptybucketinterface => emptybucketinterface