Typescript timer with callback function I can wait on

Question

I'm relatively new to typescript.
I'm trying to create a timer (or use a ready to use one if you know any) that will allow me to perform an operation several times (For example: Perform a UI operation like fade on every element in an array) every interval and will give me an end sign I can wait on.
So far I came with:

function delay(delay: number) {
    return new Promise(r => {
        setTimeout(r, delay);
    })
}

type timerCallback = (args: any, counter: number) => void;

class Timer {
    private _callback: timerCallback;

    constructor(callback: timerCallback) {
        this._callback = callback;
    }

    async doTimer(args: any, counter: number = 3, delayMs: number = 1000) {
        for (let i = 0; i < counter; i++) {
            await delay(delayMs);
            counter = counter - 1;
            this._callback(args, i);
            //console.log(this.counter);
        }
    }
}

And I use it like that:

public myMethod(): void {
// Show the players in the quality group
let showTimer: Timer = new Timer(this.showElement);
showTimer.doTimer(allQaulityGroupPlayersCells, allQaulityGroupPlayersCells.length, 750);
}

But I need to wait until all the iterations on the timer are over...
Any idea how can I achieve this?

T.J. Crowder · Accepted Answer · 2020-02-05 17:08:57Z

1

Wait for the promise from showTimer.doTimer to settle, eithe rusing await (in an async function) or its then/catch methods (in a non-async function).

Your myMethod is a non-async function, so:

showTimer.doTimer(/*...*/)
.then(() => {
    // It's done now
})
.catch(() => {
    // An error occurred
});

Your doTimer's promise will never be rejected, so technically you could leave off the catch handler. But so many times you see people leaving it off when the promise may, in fact, be rejected that I'm hesitant to show an example that doesn't follow the Rule Of Promises: Thou Shalt Return The Promise Chain Or Handle Rejections. ;-)

answered Feb 5, 2020 at 17:08

T.J. Crowder

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