postcode-regex.js

var tweet = "Currently chilling out at W1B 2EL, then on to WC2E 8HA or maybe even L1 8JF! :-)";

// Here's a simple regex that tries to recognise postcode-like strings. 
// See http://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdom#Validation
// for the rules on how UK postcodes are formatted.
var postcode_regex = /[A-Z]{1,2}[0-9][0-9A-Z]?\s?[0-9][A-Z]{2}/g;

var postcodes = tweet.match(postcode_regex);

console.log(postcodes);