This article has been given a more permanent home on my blog. Also, since it was first written, the development of the Promises/A+ specification has made the original emphasis on Promises/A seem somewhat outdated.
Promises are a software abstraction that makes working with asynchronous operations much more pleasant. In the most basic definition, your code will move from continuation-passing style:
getTweetsFor("domenic", function (err, results) {
// the rest of your code goes here.
| /*jslint regexp: true, maxerr: 50, indent: 2 */ | |
| (function (global) { | |
| "use strict"; | |
| function URLUtils(url, baseURL) { | |
| var m = String(url).replace(/^\s+|\s+$/g, "").match(/^([^:\/?#]+:)?(?:\/\/(?:([^:@\/?#]*)(?::([^:@\/?#]*))?@)?(([^:\/?#]*)(?::(\d*))?))?([^?#]*)(\?[^#]*)?(#[\s\S]*)?/); | |
| if (!m) { | |
| throw new RangeError(); | |
| } |
| function crc32_asm() { | |
| var table = new Uint32Array([ | |
| 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, | |
| 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, | |
| 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, | |
| 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, | |
| 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, | |
| 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, | |
| 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c, | |
| 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, |