Python-like string and array chopping

chop.js

var chop = function(list, arr) {
    var start = arr[0] || 0;
    var end = arr[1] || list.length;
    
    if (Array.isArray(list)) {
        list = list.splice(start, end - start);
        return list;
    } else if (typeof list === "string") {
        return list.substring(start, end);
    }
    return null;
};

/*
chop("spam", [1,]) => "pam"
chop("spam", [1,2]) => "p"
chop("spam", [,2]) => "sp

chop(["zero", "one", "two"], [,2]) => ["zero", "one"]
*/