Question

7

typescript - create a callback function

rated 0 times [ 8] [ 1] / answers: 1 / hits: 16416 / 8 Years ago, thu, november 3, 2016, 12:00:00

hey guys i'd like to know how to make a callback function in typescript.

I know how to do it in vanilla JS :

function mySandwich(param1, param2, callback) {

alert('Started eating my sandwich.nnIt has: ' + param1 + ', ' + param2);

callback();}



mySandwich('ham', 'cheese', function() {

alert('Finished eating my sandwich.');});

But i can't find a way to do it with TS.
you guys have an example of it?

thank you!

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raymondd

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2 Years ago

answered 8 Years ago micayla · Accepted Answer

Typescript is a superset of javascript, so any javascript code is valid typescript code.

But you can use types for safety:

function mySandwich(param1: string, param2: string, callback: () => void) {

    alert('Started eating my sandwich.nnIt has: ' + param1 + ', ' + param2);

    callback();

}



mySandwich('ham', 'cheese', function() {

    alert('Finished eating my sandwich.');

});



mySandwich('ham'); // Error: Supplied parameters do not match any signature of call target



mySandwich('ham', 'cheese', (num: number) => 4 * num); // Error: Argument of type '(num: number) => number' is not assignable to parameter of type '() => void'

(code in playground)