How to pass optional parameters while omitting some other optional parameters

Question

Given the following signature   export interface INotificationService       error message  string  title   string  autoHideAfter   number       How can I call the function error   not specifying the title parameter  but setting autoHideAfter to say 1000

User · Answer

You can do this without an interface   class myClass    public error message  string  title   string  autoHideAfter    number                      use the   operator as an optional parameter

User · Answer

As specified in the documentation  use undefined   export interface INotificationService       error message  string  title   string  autoHideAfter    number      class X       error message  string  title   string  autoHideAfter   number            console log message  title  autoHideAfter            new X   error  hi there   undefined  1000     Playground link

User · Answer

You could try to set title to null   This worked for me   error  This is the   null 1000

User · Answer

You can create a helper method that accept a one object parameter base on error arguments   error message  string  title   string  autoHideAfter   number      getError args    message  string  title   string  autoHideAfter   number          return error args message  args title  args autoHideAfter

User · Answer

This is almost the same as  Brocco  s answer  but with a slight twist  only pass optional parameters in an object   And also make params object optional    It ends up being kind of like Python s   kwargs  but not exactly   export interface IErrorParams     title   string    autoHideAfter   number     export interface INotificationService        make params optional so you don t have to pass in an empty object      in the case that you don t want any extra params   error message  string  params   IErrorParams         all of these will work as expected error  A message with some params but not others     autoHideAfter  42    error  Another message with some params but not others     title   StackOverflow     error  A message with all params     title   StackOverflow   autoHideAfter  42    error  A message with all params  in a different order     autoHideAfter  42  title   StackOverflow     error  A message with no params at all

User · Answer

Unfortunately there is nothing like this in TypeScript  more details here  https   github com Microsoft TypeScript issues 467   But to get around this you can change your params to be an interface   export interface IErrorParams     message  string    title   string    autoHideAfter   number     export interface INotificationService     error params  IErrorParams        then to call it  error  message   msg   autoHideAfter  42

User · Answer

Another approach is   error message  string  options    title   string  autoHideAfter   number      So when you want to omit the title parameter  just send the data like that   error  the message     autoHideAfter  1      I d rather this options because allows me to add more parameter without having to send the others

User · Answer

You can specify multiple method signatures on the interface then have multiple method overloads on the class method   interface INotificationService       error message  string  title   string  autoHideAfter   number       error message  string  autoHideAfter  number      class MyNotificationService implements INotificationService       error message  string  title   string  autoHideAfter   number       error message  string  autoHideAfter   number       error message  string  param1    string number   param2   number            var autoHideAfter  number              title  string              example of mapping the parameters         if  param2    null                autoHideAfter   param2              title    lt string gt  param1                    else if  param1    null                if  typeof param1      string                     title   param1                            else                   autoHideAfter   param1                                      use message  autoHideAfter  and title here           Now all these will work   var service  INotificationService   new MyNotificationService    service error  My message    service error  My message   1000   service error  My message    My title    service error  My message    My title   1000        and the error method of INotificationService will have the following options     Playground

User · Answer

you can use optional variable by   or if you have multiple optional variable by      example   function details name  string  country  CA   address   string     hobbies  string                   In the above    name is required country is required and has a default value address is optional hobbies is an array of optional params

[typescript] How to pass optional parameters while omitting some other optional parameters?

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