Is javascript promise the same as an arraylist in java?

[babadoctor]

Title

[reniat]

Apples and oranges. a promise in JS seems to be a way to write asynchronous code (i've never written concurrent JS, so i could be wrong), while an arraylist in java is just an implementation of an abstract data type. The only semi-related aspect of arraylist is that there are concurrency concerns in that arraylists are not synchronized so you need to be careful if you have multiple threads operating on the same list.

[vorticalbox]

On 18/07/2018 at 4:35 AM, reniat said:

Apples and oranges. a promise in JS seems to be a way to write asynchronous code (i've never written concurrent JS, so i could be wrong).

Promises are like callbacks, it means that part of the code will be executed only when the promise is resolved.

 

Bare with me I'm on my phone, so say you were using nodeJs and making an api request

 

const got = require('got');

const results = got.get('http://example.com/data/123');

console.log(results)

 

Because the got request is async it will fire of the get request then move on to the console.log and you'll get undefined.

 

Now got returns a promise so

 

const got = require('got');

got.get('http://example.com/data/123').then((results) =>{

    console.log(results)

})

 

 

This will cause the event loop to wait until the promise is resolved before doing the console.log

 

What is great about promises is the  you can chain .then and what ever is returned from that function is passed to the next one.