JavaScript Rules

A few days ago I introduced a friend of mine Jorge Rocha to SPOJ an online judge system for user-submitted programs, one of the first problems that he tried was the Prime Generator it consisted in finding all primes in a given range of numbers, after some time and few different algorithms he asked me if I had any tips to help him, although he had the correct algorithm (Sieve of Eratosthenes) something was clearly missing, the solution wasn’t fast enough and I had no clue where to go from there, so as usual when a question like that comes up I resort to Mauro Persano… and obviously he knew the answer, he taught us how to apply a heuristic to the algorithm to help solve the problem and after doing so the code worked and the solution was approved.

Continue reading ‘Finding prime numbers with Javascript’ »

I’ve just finished chapter 7: Writing Efficient JavaScript by Nicholas Zakas on Steve Souders‘ new book, Even Faster Web Sites, where he presents several string optimization techniques to improve JavaScript performance and wondered which algorithm does String.indexOf method implements on JavaScript engines (aka ECMAScript engines).
A few months ago I’ve asked this question to Yahoo! fellow Douglas Crockford and he said the ECMAScript standard does not require a specific algorithm, so it could vary with each browser. You can check that on section 15.5.4.7 of Standard ECMA-262. I decided then to download the most popular open-source JavaScript engines source codes and found mainly 3 algorithms:

Continue reading ‘String searching algorithms in JavaScript engines’ »