Javascript function as argument in setTimout

Question

In the following code, "Blast Off!" displays one second after the 1 displays. But, if I change the function call to setTimeout(finish(), 1000) "Blast Off!" displays immediately after 1. Why does including the () change the timing?

let countDown= time => {
    let timer = setInterval(function(){
        console.log(time);
        time--;
        if (time==0){
            clearInterval(timer);
            let finish = ()=> {
                console.log("Blast Off!");
            }
            setTimeout(finish, 1000);   
        }
    1000);
};
let startNum = Number(prompt("What number should I start counting down from? "));
countDown(startNum);

Trying to understand the difference between setTimeout(finish, 1000) and setTimeout(finish(), 1000)

Because adding the `()` calls the function. `setTimeout` expects a function **reference**. — Dave Newton, Nov 09 '22 at 16:29

score 0 · Answer 1 · answered Nov 09 '22 at 16:29

0

When you use finish you are just telling the timeout that you want to run the finish function after 1000ms. On the other hand, when you use finish() you are calling the function, that is why it runs immediately

answered Nov 09 '22 at 16:29

Boguz

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Javascript function as argument in setTimout

1 Answers1