Using setTimeout on promise chain

Question

To keep the promise chain going, you can't use setTimeout() the way you did because you aren't returning a promise from the .then() handler - you're returning it from the setTimeout() callback which does you no good.

Instead, you can make a simple little delay function like this:

function delay(t, v) {
   return new Promise(function(resolve) { 
       setTimeout(resolve.bind(null, v), t)
   });
}

And, then use it like this:

getLinks('links.txt').then(function(links){
    let all_links = (JSON.parse(links));
    globalObj=all_links;

    return getLinks(globalObj["one"]+".txt");

}).then(function(topic){
    writeToBody(topic);
    // return a promise here that will be chained to prior promise
    return delay(1000).then(function() {
        return getLinks(globalObj["two"]+".txt");
    });
});

Here you're returning a promise from the .then() handler and thus it is chained appropriately.

---

You can also add a delay method to the Promise object and then directly use a .delay(x) method on your promises like this:

function delay(t, v) {
   return new Promise(function(resolve) { 
       setTimeout(resolve.bind(null, v), t)
   });
}

Promise.prototype.delay = function(t) {
    return this.then(function(v) {
        return delay(t, v);
    });
}


Promise.resolve("hello").delay(500).then(function(v) {
    console.log(v);
});

Or, use the Bluebird promise library which already has the .delay() method built-in.

.then(() => new Promise((resolve) => setTimeout(resolve, 15000)))

UPDATE:

when I need sleep in async function I throw in

await new Promise(resolve => setTimeout(resolve, 1000))

The shorter ES6 version of the answer:

const delay = t => new Promise(resolve => setTimeout(resolve, t));

And then you can do:

delay(3000).then(() => console.log('Hello'));

If you are inside a .then() block and you want to execute a settimeout()

            .then(() => {
                console.log('wait for 10 seconds . . . . ');
                return new Promise(function(resolve, reject) { 
                    setTimeout(() => {
                        console.log('10 seconds Timer expired!!!');
                        resolve();
                    }, 10000)
                });
            })
            .then(() => {
                console.log('promise resolved!!!');

            })

output will as shown below

wait for 10 seconds . . . .
10 seconds Timer expired!!!
promise resolved!!!

Happy Coding!