Progress

---

By now, this is what the knowledge map should look like. 30% of the concepts in this course are complete.

Refactoring if conditions

---

This takes care of the if else if vindaloop.

const getPushMessage = status => {
    if (status === "received") {
        return "Restaurant started working on your order.";
    } else if (status === "prepared") {
        return "Driver is picking up your food."
    } else if (status === "en_route") {
        return "Driver is cycling your way!";
    } else if (status === "arrived") {
        return "Enjoy your food!";
    } else {
        return "Unknown status";
    }
}

//becomes this via nullish coalescing. 
const getPushMessage = status => {
    const messages = {
        received: "Restaurant started working on your order.",
        prepared: "Driver is picking up your food.",
        en_route: "Driver is cycling your way!",
        arrived: "Enjoy your food!"
    };

    return messages[status] ?? "Unknown status";
}

Try it

---

Refactor the getStatus function and avoid using if conditions.

const getStatus = (host, user, booking) => {
    if (booking.status === "pending") {
        return `Hey ${user}, we're awaiting confirmation from ${host}.`;
    } else if (booking.status === "confirmed") {
        return `Hey ${user}, ${host} is excited to be hosting you.`;
    } else if (booking.status === "canceled") {
        return `Unfortunately ${user}, ${host} has canceled your booking request.`;
    } else if (booking.status === "done") {
        return `${host} hopes you had a great stay.`;
    } else {
        return "Unknown booking status."
    }
}

//Solution
const getStatus = (host, user, booking) => {
    const messages = {
        pending: `Hey ${user}, we're awaiting confirmation from ${host}.`,
        confirmed: `Hey ${user}, ${host} is excited to be hosting you.`,
        canceled: `Unfortunately ${user}, ${host} has canceled your booking request.`,
        done: `${host} hopes you had a great stay.`,
    }
    return messages[booking.status] ?? "Unknown booking status."
}

Implicit conversion and falsy values

---

MDN Docs The second condition in this statement will not output. Why?

const name = "Sam";
const number = 0;

if (name) {
    console.log("First condition");
}

if (number) {
    console.log("second condition")
}

These are "falsy values" - meaning they will be converted to false.

• false (is already a boolean)
• null
• undefined
• 0
• NaN
• "" (empty string)

Logical Not

---

MDN Docs

if (!true); //false
if (!false); //true

Recap

---

• Implicit conversion happens when JavaScript expects a boolean value but is given a non-boolean value.
• Implicit conversion means that JavaScript will automatically convert the value to boolean.
• Falsy values are converted to false. Everything else is converted to true.
• Most common falsy values are: false, null, undefined, 0, "", NaN.
• The logical NOT operator ! converts a boolean value to its opposite.