@neal83/typeswitch v1.0.6

TypeSwitch

Provides a TypeSwitch function in Typescript allowing you to switch on the type of the argument past into the function providing a sudo simple pattern matching function.

The Case function used within the TypeSwitch is type safe, so you can't use a String and then provide a function that uses a number as it's argument.

The TypeSwitch function can be used like this:

class MyOwnMarkerClass {
  public someProperty: string = "some property value"
}

const result = TypeSwitch(new MyOwnMarkerClass())(
    Case(Number)
      ((n: Number) => `you gave me a number and it was ${n.toString()}`),
    Case(String)
      ((s: String) => `you gave me a string ${s}`),
    Case(MyOwnMarkerClass)
      ((m: MyOwnClass) => `you gave me MyOwnClass with value ${m.someProperty}`)
);

The above result const will have the value you gave me MyOwnClass with value some property value.

TypeSwitchWithDefault

Provides the same functionality as above with the addition of a default function if all cases have not been met.

The TypeSwitchWithDefault function can be used like this:

class MyOwnMarkerClass {
  public someProperty: string = "some property value"
}

const result = TypeSwitchWithDefault(new MyOwnMarkerClass())(
    Case(Number)
      ((n: Number) => `you gave me a number and it was ${n.toString()}`),
    Case(String)
      ((s: String) => `you gave me a string ${s}`),
)(
  Default(() => 'this is the default returned value')
);

The above result const will have the value this is the default returned value.

TypeSwitch with When

When provides the TypeSwitch function a condition to match upon if using the same class for two different conditions.

As with the Case function the When function used within Case is type safe, so you can't use a String and then provide a function that uses a number as it's argument.

The TypeSwitch function can be used like this:

class MyOwnMarkerClass {
  public someProperty: string = "some property value"
}

const result = TypeSwitch(new MyOwnMarkerClass())(
    Case(Number, When(n: number => n === 36))
      ((n: Number) => `you gave me a number and it was 36`),
    Case(Number, When(n: number => n > 0))
      ((n: Number) => `you gave me a number and it was positive`),
    Case(String)
      ((s: String) => `you gave me a string ${s}`),
    Case(MyOwnMarkerClass, When(m => m.someProperty === "some property value")) //the type is inferred
      ((m: MyOwnClass) => `you gave me MyOwnClass with value ${m.someProperty}`)
);

The above result const will have the value you gave me MyOwnClass with value some property value.