TypeScript Functions Function as a parameter
Example
Suppose we want to receive a function as a parameter, we can do it like this:
function foo(otherFunc: Function): void {
...
}
If we want to receive a constructor as a parameter:
function foo(constructorFunc: { new() }) {
new constructorFunc();
}
function foo(constructorWithParamsFunc: { new(num: number) }) {
new constructorWithParamsFunc(1);
}
Or to make it easier to read we can define an interface describing the constructor:
interface IConstructor {
new();
}
function foo(contructorFunc: IConstructor) {
new constructorFunc();
}
Or with parameters:
interface INumberConstructor {
new(num: number);
}
function foo(contructorFunc: INumberConstructor) {
new contructorFunc(1);
}
Even with generics:
interface ITConstructor<T, U> {
new(item: T): U;
}
function foo<T, U>(contructorFunc: ITConstructor<T, U>, item: T): U {
return new contructorFunc(item);
}
If we want to receive a simple function and not a constructor it's almost the same:
function foo(func: { (): void }) {
func();
}
function foo(constructorWithParamsFunc: { (num: number): void }) {
new constructorWithParamsFunc(1);
}
Or to make it easier to read we can define an interface describing the function:
interface IFunction {
(): void;
}
function foo(func: IFunction ) {
func();
}
Or with parameters:
interface INumberFunction {
(num: number): string;
}
function foo(func: INumberFunction ) {
func(1);
}
Even with generics:
interface ITFunc<T, U> {
(item: T): U;
}
function foo<T, U>(contructorFunc: ITFunc<T, U>, item: T): U {
return func(item);
}
