Podcast
Questions and Answers
What does the spread operator do in JavaScript?
What does the spread operator do in JavaScript?
- Combines two objects into one
- Returns the length of an array
- Unpacks elements from an array (correct)
- Packs elements into an array
In the context of the rest parameter, where must it be placed within a function's parameters?
In the context of the rest parameter, where must it be placed within a function's parameters?
- At the beginning
- At the end (correct)
- In the middle
- After another parameter
What is the output of the following code: console.log(0 || null || 'hana');?
What is the output of the following code: console.log(0 || null || 'hana');?
- null
- 'hana' (correct)
- 0
- undefined
What will be the output of the following code: console.log('loise' && 2 && 'hana');?
What will be the output of the following code: console.log('loise' && 2 && 'hana');?
If character1.age is undefined, what will be the output after executing character1.age ??= 55000?
If character1.age is undefined, what will be the output after executing character1.age ??= 55000?
What will the console output if you execute shopingList('eggs','tomato','butter');?
What will the console output if you execute shopingList('eggs','tomato','butter');?
What does the nullish coalescing operator return when the value is 0?
What does the nullish coalescing operator return when the value is 0?
In the following collection, what would rest represent if the object is destructured: const {name, type, ...rest} = serie;?
In the following collection, what would rest represent if the object is destructured: const {name, type, ...rest} = serie;?
What will the console output if character1.age is 0 before executing character1.age ||= 55000?
What will the console output if character1.age is 0 before executing character1.age ||= 55000?
What is the output of console.log(2 || 'loise')?
What is the output of console.log(2 || 'loise')?
What will the value of 'a' be after the following code is executed: const arr = [1, 2, 3]; const [a, , c] = arr;
What will the value of 'a' be after the following code is executed: const arr = [1, 2, 3]; const [a, , c] = arr;
What is the result of executing the line 'const [a = 10, b = 20, c = 30] = numbers;' if 'numbers' is an empty array?
What is the result of executing the line 'const [a = 10, b = 20, c = 30] = numbers;' if 'numbers' is an empty array?
Which statement about array destructuring is incorrect?
Which statement about array destructuring is incorrect?
After the execution of 'let a = 1; let b = 2; [a, b] = [b, a];', what will be the values of 'a' and 'b'?
After the execution of 'let a = 1; let b = 2; [a, b] = [b, a];', what will be the values of 'a' and 'b'?
What does the function 'getMultipleValues' return when destructured as 'const [a, b, c] = getMultipleValues();'?
What does the function 'getMultipleValues' return when destructured as 'const [a, b, c] = getMultipleValues();'?
In the context of destructuring, what is the purpose of the parentheses in '({ a, b } = obj);'?
In the context of destructuring, what is the purpose of the parentheses in '({ a, b } = obj);'?
If 'const orders = ['salad','kebab','cola'];' is spread into a function, how would that function signature look?
If 'const orders = ['salad','kebab','cola'];' is spread into a function, how would that function signature look?
What will the output of 'console.log(...allorders);' be if 'allorders' is defined as 'const allorders = [...otherOrder ,...orders];'?
What will the output of 'console.log(...allorders);' be if 'allorders' is defined as 'const allorders = [...otherOrder ,...orders];'?
Which of the following correctly describes the behavior of the spread operator?
Which of the following correctly describes the behavior of the spread operator?
In the context of nested arrays, what would the value of 'c' be after the line 'const [a, [b, c], d] = nested;' where 'nested = [1, [2, 3], 4];'?
In the context of nested arrays, what would the value of 'c' be after the line 'const [a, [b, c], d] = nested;' where 'nested = [1, [2, 3], 4];'?
What is the output of the following code: for(const item of arr.entries()) {console.log(item)} if arr is ['Newt', 'Tina', 'Jacob Kowalski', 'Queenie']?
What is the output of the following code: for(const item of arr.entries()) {console.log(item)} if arr is ['Newt', 'Tina', 'Jacob Kowalski', 'Queenie']?
During what situation can you use optional chaining in JavaScript?
During what situation can you use optional chaining in JavaScript?
What will the method serie.getInfo() output when called on the serie object?
What will the method serie.getInfo() output when called on the serie object?
What does the syntax [seasonNum]: { ... } accomplish in the seasons object inside the serie object?
What does the syntax [seasonNum]: { ... } accomplish in the seasons object inside the serie object?
What will happen if arr does not exist in the code for(const [i, el] of arr.entries()) { ... }?
What will happen if arr does not exist in the code for(const [i, el] of arr.entries()) { ... }?
What is a potential drawback of using enhanced object literals for dynamic properties?
What is a potential drawback of using enhanced object literals for dynamic properties?
What is the output of the code: console.log(seasons[1].realesed.First)?
What is the output of the code: console.log(seasons[1].realesed.First)?
How can property names be computed dynamically in JavaScript objects?
How can property names be computed dynamically in JavaScript objects?
What does the getInfo method lack in the given object definition?
What does the getInfo method lack in the given object definition?
How many properties are defined in the seasons object?
How many properties are defined in the seasons object?
In the code snippet serie.getInfo?.();, what is the purpose of the ?. operator?
In the code snippet serie.getInfo?.();, what is the purpose of the ?. operator?
In the statement const keyArr = Object.keys(yourBuletJornal);, what does the Object.keys() method return?
In the statement const keyArr = Object.keys(yourBuletJornal);, what does the Object.keys() method return?
Which of the following statements is true regarding the code snippet const valuesArr = Object.values(yourBuletJornal);?
Which of the following statements is true regarding the code snippet const valuesArr = Object.values(yourBuletJornal);?
What does the code snippet const values =Object.values(Object.keys(Object.values(openinghours))); calculate?
What does the code snippet const values =Object.values(Object.keys(Object.values(openinghours))); calculate?
In the code snippet for(const [day,{open,close}] of enteries){ console.log(day,open,close); }, what is the purpose of the open and close variables within the loop?
In the code snippet for(const [day,{open,close}] of enteries){ console.log(day,open,close); }, what is the purpose of the open and close variables within the loop?
What is the main purpose of the ?. operator in the code console.log(serie.seasons['6']?.realesed.First); ?
What is the main purpose of the ?. operator in the code console.log(serie.seasons['6']?.realesed.First); ?
What is the purpose of the ?? operator in the code serie.risoto?.(10,12)??console.log('the method does not exist');?
What is the purpose of the ?? operator in the code serie.risoto?.(10,12)??console.log('the method does not exist');?
What is the primary purpose of the code for(const k of Object.keys(yourBuletJornal)){ console.log(k); }?
What is the primary purpose of the code for(const k of Object.keys(yourBuletJornal)){ console.log(k); }?
Flashcards
Array Destructuring
Array Destructuring
A syntax to unpack values from arrays into distinct variables.
Default Values in Destructuring
Default Values in Destructuring
Assigns default values when the destructured variable is undefined.
Rest Operator
Rest Operator
Syntax to collect the remaining elements of an array into a new array.
Swapping Variables
Swapping Variables
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Returning Multiple Values
Returning Multiple Values
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Nested Arrays
Nested Arrays
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Object Destructuring
Object Destructuring
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Spread Operator
Spread Operator
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Shallow Copy of Objects
Shallow Copy of Objects
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Iterables
Iterables
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Array.entries()
Array.entries()
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Destructuring in Loops
Destructuring in Loops
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Enhanced Object Literals
Enhanced Object Literals
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Computed Property Names
Computed Property Names
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Template Literals
Template Literals
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Optional Chaining
Optional Chaining
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Method Definition in ES6
Method Definition in ES6
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Array Iteration
Array Iteration
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Object Property Shorthand
Object Property Shorthand
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Objects in JavaScript
Objects in JavaScript
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Rest Parameter
Rest Parameter
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Rest Pattern
Rest Pattern
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Nullish Coalescing Operator
Nullish Coalescing Operator
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Logical Assignment Operator
Logical Assignment Operator
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For...of Loop
For...of Loop
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Short-Circuiting
Short-Circuiting
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Array Spread Syntax
Array Spread Syntax
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Function with Rest Parameters
Function with Rest Parameters
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Object.keys()
Object.keys()
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Object.values()
Object.values()
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Object.entries()
Object.entries()
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Looping Objects
Looping Objects
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Destructuring Assignment
Destructuring Assignment
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Accessing Nested Properties
Accessing Nested Properties
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Study Notes
Array Destructuring
-
ES6 feature for extracting values from arrays
-
Example:
const arr = [1, 2, 3]; const [x, y, z] = arr;assigns 1 to x, 2 to y, and 3 to z -
Skipping elements:
const [a, , c] = arr;skips the second element -
Default values:
const [a = 10, b = 20, c = 30] = numbers;provides default values if the array doesn't have enough elements -
Rest parameter:
const [a, b, ...rest] = numbers;captures the first two elements and the rest into a new array calledrest
Returning Multiple Values
-
Functions can return multiple values as an array
-
Example:
function getMultipleValues() { return [10, 20, 30]; } -
Destructuring the returned array:
const [a, b, c] = getMultipleValues();extracts the values
Nested Arrays
- Destructuring nested arrays is possible, using nested array indexing.
- Example:
const nested = [1, [2, 3], 4]; const [a, [b, c], d] = nested;
Destructuring Objects
-
Assigning object properties to variables
-
Example:
const obj = { a: 23, b: 7, c: 14 }; { a, b } = obj; -
Swapping or Mutating Data
- Example:
let a = 111; let b = 999; [a,b] = [b,a];//Swaps variables
- Example:
-
Using the nullish coalescing operator to provide defaults.
- Example:
const loveNum = aurthorLovetoMerline ?? 100;//Returns loveNum value or a default 100
- Example:
Spread Operator
- Used to expand array elements into function arguments
- For example:
const orders = ['salad', 'kebab', 'cola'];
const restaurantOrder = function(a, b, c) {
console.log('here are your ${a} and ${b} with ${c}');
};
restaurantOrder(...orders);
- Creating shallow copies of arrays and objects
Iterables/Shallow Copies
-
Arrays, strings, maps and sets are iterables, the
...operator works for iterables -
const newArr = [ ...str, ...sld];creates an array based on string values
Rest Parameters for Functions
- The rest parameter syntax (
...) allows a function to accept an unlimited number of arguments - Example:
const shopingList = function(...concepts) {
console.log(concepts);
};
shopingList('eggs', 'tomato', 'butter');
Enhanced Object Literals
- Computed property names can be used to dynamically assign keys based on expressions - Example: const seasons = { [seasonNum[0]]: { episode: 13 }};
Optional Chaining
- Allows safe navigation through deeply nested object properties Example
console.log(serie.seasons['6']?.realesed.First);
For...Of Loops
-
Iterates over the elements of an iterable object (e.g., array, string)
-
Example:
const arr = ['Newt', 'Tina', 'Jacob Kowalski', 'Queenie']; for (const item of arr){console.log(item)} -
The
entries()method in for..of allows to enumerate the index and the value- Example:
for (const [i, el] of arr.entries()) { // [index, value] pair console.log('index ${i} has the value ${el}'); }
Looping over Properties
-
Used to iterate property names of an object:
- Example:
const yourBuletJornal = {texture: {size:10,colore:'lightGreen'}, margins:{size:'25cm }} for(const k of Object.keys(yourBuletJornal)) { console.log(k) }
- Example:
-
Object.keys(): Returns an array of an object property names; -
Object.values(): Returns an array of object values; - Example:const valuesArr = Object.values(yourBuletJornal); -
Object.entries(): Returns an array of key-value pairs of an object. Example:const enteries = Object.entries(openinghours);
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Description
This quiz explores the ES6 feature of array destructuring in JavaScript. You will learn how to extract values from arrays, skip elements, use default values, and work with nested arrays. Test your understanding of returning multiple values and destructuring objects as well.
