function getPath(x, p) // x: nested lists // p: path

const xlists = require('extra-lists'); var x = [['a', 'b', 'c'], [2, 4, 6]]; var y = [['x', 'e', 'f'], [x, 10, 12]]; xlists.getPath(y, ['e']); // → 10 xlists.getPath(y, ['x', 'b']); // → 4 xlists.getPath(y, ['x', 'b', 'c']); // → undefined