void function in typescript code example

Example 1: typescript pass a function as an argunetn

class Foo {
    save(callback: (n: number) => any) : void {
        callback(42);
    }
}
var foo = new Foo();

var strCallback = (result: string) : void => {
    alert(result);
}
var numCallback = (result: number) : void => {
    alert(result.toString());
}

foo.save(strCallback); // not OK
foo.save(numCallback); // OK

Example 2: void in ts

// Similar to languages like Java, void is used where there is no data. 
// For example, if a function does not return any value then you can 
// specify void as return type.
function sayHi(): void { 
    console.log('Hi!')
} 

let speech: void = sayHi(); 
console.log(speech); //Output: undefined