Advanced Concepts Problems

Question 1

All:
https://javascriptweblog.wordpress.com/2010/07/06/function-declarations-vs-function-expressions/

Answer 1

https://javascriptweblog.wordpress.com/2010/07/06/function-declarations-vs-function-expressions/

Question 2

Hoisting and the var Statement:
https://launchschool.com/lessons/43f23069/assignments/39f50f91

Answer 2

https://launchschool.com/lessons/43f23069/assignments/39f50f91

Question 3

Strict Mode
Problem at bottom of page
https://launchschool.com/gists/406ba491

Answer 3

https://launchschool.com/gists/406ba491

Question 4

Closures:
https://launchschool.com/lessons/43f23069/assignments/9362d2cf

Answer 4

https://launchschool.com/lessons/43f23069/assignments/9362d2cf

Question 5

Private data,
at bottom of page:
https://launchschool.com/lessons/43f23069/assignments/3df10c91

Answer 5

https://launchschool.com/lessons/43f23069/assignments/3df10c91

Question 6

IIFE
https://launchschool.com/lessons/43f23069/assignments/69bab49c

Answer 6

https://launchschool.com/lessons/43f23069/assignments/69bab49c

Question 7

Shorthand:
https://launchschool.com/lessons/43f23069/assignments/c6c682cd

Answer 7

https://launchschool.com/lessons/43f23069/assignments/c6c682cd

Question 8

do this but with no conditional statements

Answer 8

https://launchschool.com/exercises/81b953d7?track=javascript

Question 9

do this (doesn’t work so good with hidden data)
https://launchschool.com/exercises/d30df1f2?track=javascript

Answer 9

https://launchschool.com/exercises/d30df1f2?track=javascript

Question 10

Advanced concepts quiz:
https://launchschool.com/quizzes/a669620d

Answer 10

https://launchschool.com/quizzes/a669620d

Question 11

What does this do?
var foo = 10;

function bar() {
if (foo > 20) {
var foo = 50;
}

console.log(foo);
foo += 10;
}

bar();
bar();
bar();

Answer 11

The declaration for foo on line 5 of the original code gets hoisted to a function-scoped variable, foo, that shadows the foo variable on line 2. Since we’re not initializing the variable inside bar, its value is undefined, and that’s what gets logged each time we execute line 8 in the original code.

function bar() {
var foo;
if (foo > 20) {
foo = 50;
}

console.log(foo);
foo += 10;
}

var foo;
foo = 10;

bar();
bar();
bar();

Question 12

The following code has console.log calls on lines 1, 4, 8, 10, and 16. In what sequence will those 5 log calls execute? (or not at all?)

console.log(foo());

function foo() {
console.log(‘Waiting for bar!’);
}

function foo() {
console.log(foo);
function bar() {
console.log(‘bar again’);
}

bar();

function bar() {
console.log(‘bar again and again’);
}
}

Answer 12

8 16 1

Question 13

what does the arguments keyword within a function reference?

Answer 13

An array like object {‘0’: arg1, etc}

Question 14

Explain in detail what lines 7 and 8 of this code are doing.

let obj = {
foo: ‘foo’,
qux: ‘qux’,
bar: ‘bar’,
};

let obj2 = {…obj};
let { …obj3 } = obj;

Answer 14

On line 7, {…obj} on the right side of the assignment operator uses spread syntax to separate obj into its properties. The brackets that wrap …obj use object literal syntax to create a new object from the properties of the original obj. On the left side of the assignment operator, a new variable called obj2 is declared. The object that was created with object literal syntax is assigned to this new variable. In summary, line 7 made a shallow copy of obj.

On line 8, on the left side of the assignment operator, object destructuring is used to separate the properties of obj. However, the only variable that’s created is using rest syntax to take all of the spread out properties and re-collect them into obj3. Line 8 is also making a shallow copy of obj.

Question 15

Write a function that takes 5 string arguments, and returns an object with 3 properties:

first: the first argument
last: the last argument
middle: the middle 3 arguments as a sorted array
After writing the function, write some code to call the function. The arguments you provide should come from an array. You should create local variables named first, last, and middle from the return value.

Use shorthand syntax wherever you can

Answer 15

function qux(first, middle1, middle2, middle3, last) {
return {
first,
last,
middle: [middle1, middle2, middle3].sort(),
};
}

let arr = [“Fluffy”, “Pudding”, “Mister”, “Ben”, “Butterscotch”];
let { first, last, middle } = qux(…arr);