Very Basic of Function Programming in JS

fp.js

var stream = {
    map: function (list, fn) {
        var newList = [];
        for (item in list) {
            var mappedItem = fn(list[item]);
            newList.push(mappedItem);
        }
        return newList;
    },
    filter: function (list, predicate) {
        var newList = [];
        for (item in list) {
            if (predicate(list[item])) {
                newList.push(list[item]);
            }
        }
        return newList;
    }
}

var list = [1, 3, 5, 8];
console.log("Actual Items: " + list);

var mappedItems = stream.map(list, function (item) {
    return item * 3;
});
console.log("Mapped Items: " + mappedItems);


var filteredItems = stream.filter(list, function (item) {
    return (item % 2) == 0;
});
console.log("Filtered Items: " + filteredItems);