How to pass optional parameters while omitting some other optional parameters?
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);
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});
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:
nameis requiredcountryis required and has a default valueaddressis optionalhobbiesis an array of optional params