I want an asynchronous function to run at a maximum rate of once a second.

async function update(){
    await wait_for_response();
}
setInterval(update, 1000);

In the above code, if the function takes longer than a second, the next update begins before the last has finished.

If update() takes longer than 1 second, I want the next update to wait until the last update is finished, running immediately afterwards.

Is there a simple built-in method or standard practice for implementing this?

I want an asynchronous function to run at a maximum rate of once a second.

async function update(){
    await wait_for_response();
}
setInterval(update, 1000);

In the above code, if the function takes longer than a second, the next update begins before the last has finished.

If update() takes longer than 1 second, I want the next update to wait until the last update is finished, running immediately afterwards.

Is there a simple built-in method or standard practice for implementing this?

• javascript
• node.js

2 Answers 2

I think that setTimeout would be a better choice in this case:

async function update() {
     const t1 = new Date();
     await wait_for_response();
     setTimeout(update, Math.max(0, 1000 - new Date + t1));
}
update();

This simple construct using promise chaining can handle it for you:

let lastPromise = Promise.resolve();
function update() {
  lastPromise = lastPromise.then(wait_for_response, wait_for_response);
}

setInterval(update, 1000);

If we're worried about the chain growing unbounded, we can use this version:

let lastPromise = Promise.resolve();
function update() {
  const p = lastPromise;
  function cleanup() {
    if (lastPromise === p) {
       lastPromise = Promise.resolve();
    }
  }
  lastPromise = lastPromise
    .then(wait_for_response, wait_for_response)
    .then(cleanup, cleanup);
}

setInterval(update, 1000);