using setTimeout synchronously in JavaScript

Question

I have the following scenario:

setTimeout(\"alert(\'this alert is timedout and should be the first\');\", 5000);
alert(\"this should be the second one\");


        

Answer 1

I came in a situation where I needed a similar functionality last week and it made me think of this post. Basically I think the "Busy Waiting" to which @AndreKR refers, would be a suitable solution in a lot of situations. Below is the code I used to hog up the browser and force a wait condition.

function pause(milliseconds) {
	var dt = new Date();
	while ((new Date()) - dt <= milliseconds) { /* Do nothing */ }
}

document.write("first statement");
alert("first statement");

pause(3000);

document.write("<br />3 seconds");
alert("paused for 3 seconds");

Keep in mind that this code acutally holds up your browser. Hope it helps anyone.

Answer 2

I think you have to make a promise and then use a .then() so that you can chain your code together. you should look at this article https://developers.google.com/web/fundamentals/primers/promises

Answer 3

No, as there is no delay function in Javascript, there is no way to do this other than busy waiting (which would lock up the browser).

Answer 4

Is the code contained in a function?

function test() {
    setTimeout(...);     

    // code that you cannot modify?
}

In that case, you could prevent the function from further execution, and then run it again:

function test(flag) {

    if(!flag) {

        setTimeout(function() {

           alert();
           test(true);

        }, 5000);

        return;

    }

    // code that you cannot modify

}

Answer 5

Using ES6 & promises & async you can achieve running things synchronously.

So what is the code doing?

 1. Calls setTimeOut 1st inside of demo then put it into the webApi Stack
 2. Creates a promise from the sleep function using the setTimeout, then resolves after the timeout has been completed;
 3. By then, the first setTimeout will reach its timer and execute from webApi stack. 
 4. Then following, the remaining alert will show up.


function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function demo() {
  setTimeout("alert('this alert is timedout and should be the first');", 5000);
  await sleep(5000);
  alert('this should be the second one');
}
demo();

Answer 6

ES6 (busy waiting)

const delay = (ms) => {
  const startPoint = new Date().getTime()
  while (new Date().getTime() - startPoint <= ms) {/* wait */}
}

usage:

delay(1000)