Obfuscated base transform

b3b7.js

h = (n = prompt("in base-3: ")).length - 1;
b = +(o = []);
l = (m = Math).log;

for(i = h; i + 1; i--) b += m.pow(3,i) * n[h - i];

for(p = (b + "").length * l(10) / l(7) | 0; p+1;)
	o.push(b / m.pow(7, p--) | 0),
	b -= o[o.length - 1] * m.pow(7, p+1);

alert("in base-7: " + o.join("").substr(!o[0]));