ho.js

function each(array, f) {
    for(var i = 0; i < array.length; i++) {
        f(array[i]);
    }
}

function map(array, f) {
    var acc = [];
    each(array, function(x) {
        acc.push(f(x));
    });
    return acc;
}

function filter(array, p) {
    var acc = [];
    each(array, function(x) {
        if (p(x)) {
            acc.push(x);
        }
    });
    return acc;
};

function odd(x) {
    return x % 2 === 1;
}

filter([0,1,2,3,4,5], odd);

function compose(f, g) {
    return function(x) {
        return f(g(x));
    };
}

function f(x) { return x + 1; }

function g(x) { return x * 2; }

var fOfG = compose(f, g);

var toastTypes = {
    white: {time: 30},
    wheat: {timed: 60}
};

var Toaster = function() {
    var handle;
    return {
        toast: function (time, toast) {
            handle = setTimeout(function () {
                console.log ("Your toast is ready");
                handle = undefined;
            }, time);
            console.log("Toasting.");
        },
        cancel: function () {
            if (handle) {
                console.log("Here's your partially toasted toast.");
                clearTimeout (handle);
                handle = undefined;
            } else {
                console.log ("You're not toasting anything!");
            }
        }
    };
};

function reduce(array, f, acc) {
    var temp = acc;
    for (var i = 0; i < array.length; i++) {
        temp = f(temp, array[i]);
    }
    return temp;
}

function mapWithReduce(array, f) {
    return reduce(array, function(acc, next) {
        acc.push(f(next));
        return acc;
    }, []);
}

// A "predicate" is a function that returns true or false.
function max(array, predicate) {
    return reduce(array, function(next, acc) {
        return predicate(acc, next) ? next : acc;
    }, array[0]);
}

var people = [
    {first: "", last: "Lehman"}, {first: "David", last: "Tran"}
];

max(people, function(previous, next) {
    return (previous.first.length + previous.last.length) < (next.first.length + next.last.length);
});

function longestWord(sentence) {
    return max(sentence.split(" "), function(prev, next) {
        return next.length > prev.length;
    });
}

longestWord("the quick brown fox jumped over the lazy dog");