simple general cache function.

cache.js

var stats = {
    hit: 0, miss: 0
};

exports.LRU = function(size,k_match) {
    var tbl=[];
    if (!k_match) k_match=function(k1,k2) {
        if (k1.length!=k2.length)
            return false;
        for (var i=0; i<k1.length; i++)
            if (k1[i]!==k2[i]) return false;
        return true;
    }
    return function() {
        var k=[];
        k.push.apply(k,arguments);
        var f=k.shift();
        for (var i=tbl.length-1; i>=0; i--) {
            var r=tbl[i];
            if (r.f===f && k_match(r.k,k)) {
                while (i<tbl.length-1) {
                    tbl[i]=tbl[i+1]; i++;
                }
                tbl[tbl.length-1]=r;
                stats.hit++;
                return r.v;
            }
        }
        var v=f.apply(null,k);
        if (tbl.length>=size) tbl.shift();
        tbl.push({f:f,k:k,v:v});
        stats.miss++;
        return v;
    };
};

exports.stats = stats;
/*
  general cache function.

  Usage: 
    var cache = require('./cache.js');
    var cached = cache.LRU(100); // 100 LRU entries.

    ...

    // you can substitute "some_func(arg1,arg2)" for below.
    var result = cached(some_func,arg1,arg2); 

  Note:
    while you can put different types of functions 
     (i.e. number of arguments) into a same cache,
    it's recommended to separate caches by function types
      as long as space issues are not concerned.
*/