stagger-calls.ts

/**
 * Calls the given list of promises in sequence, ensuring a minimum
 * delay of `staggerMs` between calls. 
 *
 * @param funcs Array of promises to call.
 * @param staggerMs The minimum time between promise calls. If a
 * promise runs longer than this, the next one is fired as soon as the
 * previous is done.
 */
export async function staggerCalls(funcs: (() => Promise<any>)[], staggerMs: number) {
    for (let index = 0; index < funcs.length; index++) {
        const element = funcs[index]

        const start = Date.now()
        await element()

        // Delay next iteration
        if (Date.now() - start < staggerMs) {
            const delayFor = staggerMs - (Date.now() - start)
            await new Promise(resolve => setTimeout(resolve, delayFor))
        }
    }
}