Control Flow Challenge Solutions

Basic Challenges

Which of the following are truthy values? (hint: try if("abc"){"console.log('I'm truthy!')"} in the JS console). truthy: 1, "abc", [], {}, -1, (1+1), 3.14159, Object falsey: "", 0

Log to the console "This is awesome!" 25 times.

 for (var i=0; i<25; i++){
     console.log("This is awesome!");
 }

Create a snippet inside of developer tools. Create snippets to do the rest of the challenges.
In your snippet, create a new variable that is an array of 4 phrases: Howdy there, OMG, javascript, and Pair Programming.

var phrases = ["Howdy there", "OMG", "javascript", "Pair Programming"];

Loop over the array and console log each phrase.

 for (var i=0; i<phrases.length; i++){
     console.log(phrases[i]);
 }

Loop over the array and log each phrase to the console if its total length is 4 or longer. Otherwise, console log that the phrase is too short.

 for (var i=0; i<phrases.length; i++){
     if (phrases[i].length >= 4){
         console.log(phrases[i]);
     } else {
         console.log("Phrase " + phrases[i] + " is too short!");
     }
 }

Come up with three different ways to break a for loop that result in three different errors. What three different errors did you get?

 for (var i=0; i<10; i--){
     console.log("This loop never ends!");
 }

 for (var i=0; i>10; i++){
     console.log("This loop's continue starts out false.")
     console.log("So code inside this loop is never executed!");
 }

 for (var i=0; i>10; i++){
     // Only functions can return.
     // Since this for loop isn't inside a function,
     // we get this error message:
     // "Uncaught SyntaxError: Illegal return statement"
     return i;
 }

Jimmy loves roller coasters, but there are a bunch of rules (ugh!) for riding:

For starters, it costs 5 tokens. Here's how we might code that:

 var tokens = 3; // Jimmy's tokens

 // Can he ride?
 if ( tokens >= 5 ) {
     console.log("Step right up!");
 } else {
     console.log("Sorry, you can't ride.");
 }

Edit the code above to check the following additional Requirements:

a. Must be at least 4ft tall

 var tokens = 3; // Jimmy's tokens
 var height; // Jimmy's height in feet

 // Can he ride?
 if ( tokens >= 5 && height >= 4) {
     console.log("Step right up!");
 } else {
     console.log("Sorry, you can't ride.");
 }

b. Must be at least 12 years old

 var tokens = 3; // Jimmy's tokens
 var height; // Jimmy's height in feet
 var age; // Jimmy's age in years

 // Can he ride?
 if ( tokens >= 5 && height >= 4 && age >=12) {
     console.log("Step right up!");
 } else {
     console.log("Sorry, you can't ride.");
 }

c. Replace the prevoius rule: now riders under 12 must be accompanied by an adult

```
var tokens = 3; // Jimmy's tokens
var height;     // Jimmy's height in feet
var age;         // Jimmy's age in years
var hasAdult;     // bool - does Jimmy have an adult?

// Can he ride?
if ( tokens >= 5 && height >= 4 ) {
    if (age >= 12 || hasAdult){
        console.log("Step right up!");
    } else {
        console.log("Sorry, you can't ride.");
    }
} else {
    console.log("Sorry, you can't ride.");
}
```




d. (If the boss isn't looking, you can sneak in!)

```
var tokens = 3; // Jimmy's tokens
var height;     // Jimmy's height in feet
var age;         // Jimmy's age in years
var hasAdult;     // bool - does Jimmy have an adult?
var isLooking;     // bool - is the boss looking?

// Can he ride?
if (!isLooking){
    console.log("Step right up!");
} else {
    if ( tokens >= 5 && height >= 4 ) {
        if (age >= 12 || hasAdult){
            console.log("Step right up!");
        } else {
            console.log("Sorry, you can't ride.");
        }
    } else {
        console.log("Sorry, you can't ride.");
    }
}
```



e. Riders with a park pass get in free.

```
var tokens = 3; // Jimmy's tokens
var height;     // Jimmy's height in feet
var age;         // Jimmy's age in years
var hasAdult;     // bool - does Jimmy have an adult?
var isLooking;     // bool - is the boss looking?
var hasPass;     // bool - does Jimmy have a park pass?

// Can he ride?
if (!isLooking){
    console.log("Step right up!");
} else {
    if ( (tokens >= 5 || hasPass) && height >= 4 ) {
        if (age >= 12 || hasAdult){
            console.log("Step right up!");
        } else {
            console.log("Sorry, you can't ride.");
        }
    } else {
        console.log("Sorry, you can't ride.");
    }
}
```

Stretch Challenges

In a snippet, create a new variable that is an array containing 5 objects, each of which has the keys name and age. You can make up the names and ages for your objects.

 var pets = [
     { name: "Abra", age: 2 },
     { name: "Benji", age: 4 },
     { name: "Chairman Meow", age: 14 },
     { name: "Dandelion", age: 1 },
     { name: "Evie", age: 6 }
 ]

Log to the console the name value of each object.

 for (var i=0; i<pets.length; i++){
     console.log(pets[i]["name"]);
     // or
     // console.log(pets[i].name);
 }

Create and log an array with the age of each object in months (assume the original ages were in years).

 var petAges = [];
 for (var i=0; i<pets.length; i++){
     petAges.push(pets[i]["age"]*12);
     // or
     // petAges.push(pets[i].age*12);
 }
 console.log(petAges);

Find and log the sum of the ages.

 var sum = 0;
 for (var i=0; i<petAges.length; i++){
     sum = sum + petAges[i];  // or sum += petAges[i]
 }
 console.log(sum);

Log to the console only the name of the oldest person.

 // pets are people too >.<
 var oldest = pets[0]; // start by assuming first pet is oldest
 for (var i=0; i<pets.length; i++){
     if (pets[i].age > oldest.age){  // or pets[i]["age"], oldest["age"]
         oldest = pets[i];     // update when assumption is proven false
     }
 }
 console.log(oldest.name);  // or oldest["name"]

Log to the console the index of each element in the array.

 for (var i=0; i<pets.length; i++){
     console.log(i);
 }

Create and log an array containing only the objects with an age over 20.

var oldPets = [];
for (var i=0; i<pets.length; i++){
    if (pets[i]["age"] > 20){  // or pets[i].age
        oldPets.push(pets[i]);
    }
}
console.log(oldPets)

Create and log an array of all the names, in which any names that begin with a consonant are upper case.

var consonants = ["b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "n", "p", "q", "r", "s", "t", "v", "w", "x", "z"];
// or var consonants = "bcdfghjklmnpqrstvwxz".split("");
var names = [];
for (var i=0; i<pets.length; i++){
    if (consonants.indexOf(pets[i]["name"]) === -1){  // or pets[i].name
        names.push(pets[i]["name"]);
    } else {
        names.push(pets[i]["name"].toUpperCase());
    }
}
console.log(names);

Create and log an array that is the original array in a random order.

Note: A good algorithm is Fisher-Yates, which is not the algorithm below.

var shuffledPets = [];

// start off by copying everything into the new array
// so we don't mess up the order of pets
for (var i=0; i<pets.length; i++){
    shuffledPets.push({ name: pets[i]["name"], age: pets[i]["age"]});
}

var temp;
for (var i=0; i<shuffledPets.length; i++){
    // swap shuffledPets[i] with pet at a random other index from the rest of the array
    temp = shuffledPets[i];
    randIndex = Math.floor(Math.random()*(shuffledPets.length));
    shuffledPets[i] = shuffledPets[randIndex];
    shuffledPets[randIndex] = temp;
}

console.log(shuffledPets);