Pause/Timeout in async.forEach NodeJS

Question

So lets say fruits is an array containing 4 items What I expected was that the code below would print fruit with a 4 second delay between each fruit.

var fruits = ['blueberries', 'strawberries', 'mango', 'peaches'];
async.forEach(fruits, functions(fruit, next) { 
     setTimeout(function() {
          console.log(fruit);
     }, 4000);
})

The actual behaviour is that it waits 4 seconds, and then prints the entire list. :\ Does anybody know how to achieve my expected behaviour?

Read the documentation. You want async.series, and you need to actually call the callback. — SLaks
– SLaks, Commented Aug 10, 2015 at 22:12
Sorry I forgot to add the callback, I was just typing up a quick example. But thank you! :) — koikoi
– koikoi, Commented Aug 11, 2015 at 15:20

user400654 · Accepted Answer · 2015-08-10 22:19:16Z

10

async.forEach runs through the array in parallel, meaning it will run the function for each item in the array immediately, and then when all of them execute the callback, the callback function (that you failed to include) will be called.

In your case, you want to run through the array one at a time, or, in a series, so you'll need the .eachSeries method.

var fruits = ['blueberries', 'strawberries', 'mango', 'peaches'];
async.eachSeries(fruits, function (fruit, next) { 
     setTimeout(function() {
          console.log(fruit);
          next(); // don't forget to execute the callback!
     }, 4000);
}, function () {
     console.log('Done going through fruits!');
});

answered Aug 10, 2015 at 22:19

user400654

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