具有多个参数的函数的JavaScript缓存返回值

Question

I'm going through John Resig's snippets on advanced JavaScript . On #19 he mentions a method to cache the return value of a function. What's the best way to cache the return value of a function that has more than one parameter?

There has to be a much better way than stringify-ing the recieved arguments and using that as the key for the cache object:

function $$(selector, el) {
    var cacheKey = JSON.stringify(arguments);
    if ($$.cache[cacheKey]) return $$.cache[cacheKey];

    return ($$.cache[cacheKey] = NodeListToArray( (el || document).querySelectorAll(s) ));
}
$$.cache = {};

Answer 1

You could use a custom hash function that can operate on objects. But hash functions cause collisions and would require significantly more code than your simple example.

Or you could make the cache n-dimensional, where n is the number of arguments. So essentially this:

function $$(selector, el) {
    if ($$.cache[selector] && $$.cache[selector][el])
        return $$.cache[cacheKey][el];
    // etc.

That assumes that both selector and el are able to be used as object keys. You may need to stringify them in another manner.

Answer 2

Just consider an array element,

JSON (JavaScript Object Notation) works with generic platform, so for easy use you must create a function for your use,

Here, $$.cache[0] is your easy way after reading the cachekey ,

If we make thing more easy, we might have security problem later.

I hope this will satisfy your requirement :)