you can write:

if (loading) {
 let time = 0;
 setTimeout(() => {
  switch(time) {
   case 2:
    alert("please wait...");
    break;
   case 5:
    alert("loading...");
    break;
   case 10:
    alert("sorry, please wait...");
    break;
  }
  time++;
 }, 1000);
}

In your specific case, you might do the following:

1. You need to correct your syntax. Functions are invoked by using () following the namespace. E.g. greet1()
2. Create a counter-based state (since it seems like your messages vary based on the "duration"). This allows us to determine the "time" that has passed.

const [downloadStatus, setDownloadStatus] = useState(0);

3. Add a onClick listener to trigger the download.

const messageDownloadPairs = { 
  1: ["Message1", 0],
  2: ["Message2", 10 * 1000]
  3: ["Message3", 20 * 1000]
}
const getDownloadMessageTimePair = (status) => 
  messages[Math.min(status, Object.values(messages).length)]

with the following jsx under return

<button onClick={invokeDownload}>{getDownloadMessage(downloadStatus)[0]}</button>

where invokeDownload follows the signature

const invokeDownload = () => {
  // Your download code here.
  setDownloadStatus(1) // Notifying the component that the download has started.
}

4. Create a function checkDownloadStatus to check if the download has completed. You can find some examples here
5. Use the hook useEffect to handle timeouts, and state updates.

useEffect(() => { 
  const downloadComplete = checkDownloadStatus()

  if (!downloadComplete) { 
    const newDownloadStatus = downloadStatus + 1
    setTimeOut(
      () => setDownloadStatus(newDownloadStatus), 
      getDownloadMessageTimePair(downloadStatus)[1]
    )
  }
}, [downloadStatus])

With this, you have a "progress-supported" button to track your csv download. I'll update this when I get more information on the specifics of your project.

I am not sure how is your code in React but in simple JS it works. Just tweak it for your need. Updated: added ability to write inside message div.

var message = document.getElementById("message");
function greet1() {
 message.innerHTML = "please wait..";
}
function greet2() {
   message.innerHTML= "loading";
}
function greet3() {
  message.innerHTML= "sorry, please wait...";
}
var loading = true;
    if (loading) {
      setTimeout(() => {
        greet1();
      }, 0);
      setTimeout(() => {
        greet2();
      }, 2000);
      setTimeout(() => {
        greet3();
      }, 3000);
    }

<div id="message" ></div>