gunnarsteinn.com

UPDATE: Adrian Quark has a much safer approach for the cache in his comment. I guess I should have tested mine better with other functions than the computational ones I was doing

A short Javascript function I made in a project to cache result from functions in Javascript. You can use this function where it makes sense to cache.

The cache method

cacheMethod.cache = {};

function cacheMethod(context, fn) {
	var funcName = fn.toString();
	funcName = funcName.substr('function '.length);
	funcName = funcName.substr(0, funcName.indexOf('('));

	context[funcName] = function() {

		if (cacheMethod.cache[funcName] == null)
			cacheMethod.cache[funcName] = {};

		// Create a unique key of parameters
		var key = Array.slice.call(arguments).join('|');
		if (cacheMethod.cache[funcName][key] == null)
			cacheMethod.cache[funcName][key] = fn.apply(this, arguments);

		return cacheMethod.cache[funcName][key];
	};
}

Usage
If we have a function like isPrime borrowed from John Resig:

function isPrime( num ) {

  var prime = num != 1; // Everything but 1 can be prime
  for ( var i = 2; i < num; i++ ) {
    if ( num % i == 0 ) {
      prime = false;
      break;
    }
  }

  return prime;
}

we can make the isPrime function cache-able with a single line of:

cacheMethod(this, isPrime);

No when we try to call the isPrime 100 times with a large prime number, this first round is calculated and all subsequent rounds use the cache. You can see the difference by removing the cacheMethod line.

for (var i=0; i<100; i++)
		document.write(isPrime(58750291)+'<br/>');

Full example here: cache.html.