Typescript function with function as parameter

Question

I want to create a generic function that repeats tasks a certain number of times. It should receive another function and repeate it x times as the user wishes.

My generic function:

export async function executeTask(task: (...args: any[]) => any, times: number) {
    // Validate the repeat parameter
    if (times <= 0 || !Number.isInteger(times))
        throw new Error('The repeat parameter should be a positive integer.');

    // Tasks promises results
    const tasksResults: Promise<any>[] = [];

    // Initialize the repeat counter
    let cycle = 0;
    while (cycle < times) {
        cycle++;
        // Add each task promise to the promises array
        tasksResults.push(task());
    }

    // Only return when all promises has resolved
    return Promise.all(tasksResults);
}

But the function I want to repeat has some optional parameters. See the func. signature:

export async function executeSpeedTest(
    targetServerId?: number,
    outputFormat?: OutputFormat,
    outputUnit?: OutputUnit,
    showProgress?: boolean
) { }

The issue is that cannot call the repeater function and pass the function to be repeated with my optional params:

const tasksResults = await executeTask(executeSpeedTest(18104), 3);

I receive the error:

Argument of type 'Promise' is not assignable to parameter of type '(...args: any[]) => any'. Type 'Promise' provides no match for the signature '(...args: any[]): any'.ts(2345)

It only works like this:

const tasksResults = await executeTask(executeSpeedTest, 3);

I'm struggling on how I can use one wrapper function to repeat whatever other function and still being able to pass the inner function parameters.

Thank you very much.

Chris Gilardi · Accepted Answer · 2021-06-22 23:39:30Z

1

How about running the code like this?

const tasksResults = await executeTask(() => executeSpeedTest(18104), 3);

This should work, since it's passing in a function that your executeTask function will call. The reason it doesn't work like this:

await executeTask(executeSpeedTest(18104))

is because you are calling executeSpeedTest when that line is executed, meaning it is taking the result of executeSpeedTest, which in this case appears to be a Promise.

Switching to the arrow function will ensure the code is only called when your calling function calls task().

answered Jun 22, 2021 at 23:39

Chris Gilardi

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2 Comments

Chris Gilardi Over a year ago

Glad it helped! If you could mark my answer as the correct answer, that'd help future readers find the question!

Daniel Over a year ago

I still don't have enough reputation to cast a vote.

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