Lightweight implementation of promises

Question

I am building a simple charting tool. When a user chooses a data source and a chart type, both the data and the script for the specific chart (.js) are loaded and then the code renders the chart.

Currently I use the following sequence:

1. Load the chart script
2. Load the data
3. Render the chart

To improve performance, I'd like to implement promises and load script and data in parallel. A library like jQuery is too big for my needs (the point of the question is not to argue on this), are there more lightweight solutions? Maybe a 1-2 kb library, or a tutorial? Again, this is a very basic implementation with just two actions in parallel.

[Update] I upvoted all the replies as they all look excellent. I'll report back after I do some more testing.

Answer 1

I strongly suggest using an implementation of the Promises/A specification, which is becoming the standard way of doing promises in JavaScript. Promises work better when everyone uses the same flavor, so it's in everyone's interest to use compatible implementations.

Q is probably the most popular and fully featured implementation (it also will adapt jQuery and other incompatible promises), while when and rsvp are supposed to be more "lightweight".