Compress small Ints based off a character string

CCV.js

function intToCCV(n,c) { // Character compression value
    var c = c || "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890!?";
    var r = [0,0,0,0];
    while (n - 64 >= 0) {
        var pos = 2;
	r[r.length-pos] += 1;
	while (r[r.length-pos]==c.length) {
	    r[r.length-pos] = 0;
            pos += 1; // Go to next position
            if (r.length-pos in r) { // If that position is alread in the data
                r[r.length-pos] += 1; // Increment that position
            } else {
                r.unshift(1); // Otherwise add it and set it to 1
            }
	}
	n-=64;
    }
    r[r.length-1] = n;
    var f = "";
    r.forEach(function(e){
        f += c.charAt(e);
    });
    return f;
}