Asynchronous javascript with Q

Installation

npm install

Examples

Asynchronous function

node async.js

We want to access the returend value. The function returns a value asynchronous. The value is undefined when we try to access it.

Asynchronous function with Q

node async_with_q.js

The function returns a promise. When the promise gets resolved the then method gets triggered.

Chained asynchronous functions

node chained_async.js

We want to send the output of the first asynchronous function to the next one and then get the resulting value.

Chained asynchronous functions with Q

node chained_async_with_q

In the then method of the first promise we return the promise from the second function. The first promise is then resolved and can be used as the input of the second function. When the second promise resolves, the final value is accessable.

Combined asynchronous functions

node combined_async.js

We have 2 asynchronous functions. We want to get the value from both of them and then combine them.

Combined asynchronous functions with Q

node combined_async_with_q.js

We create a new asynchronous function that returns a promise that resolves both values when both of the input promises gets resolved.

Error handling with Q

node async_error

Our getData functions has an error and the promise gets rejected instead of resolved.

Chained error handling with Q

node chained_async_error.js

Again our getData fails. This time the rejected promise gets propagated through the addData function.

Combined error handling with Q

node combined_async_error.js

The error gets propagated also when the asynchronous functions are combined.