32. When you click the paragraph, what's the logged output?
A: p div
B: div p
C: p
D: div
<div onclick="console.log('div')"> <p onclick="console.log('p')"> Click here! </p> </div>A: p div
B: div p
C: p
D: div
DevScrolls
32. When you click the paragraph, what's the logged output? <div onclick="console.log('div')"> <p onclick="console.log('p')"> Click here! </p> </div> A: p div B: div p C: p D: div
Answer: A
If we click p, we see two logs: p and div. During event propagation, there are 3 phases: capturing, target, and bubbling. By default, event handlers are executed in the bubbling phase (unless you set useCapture to true). It goes from the deepest nested element outwards.
If we click p, we see two logs: p and div. During event propagation, there are 3 phases: capturing, target, and bubbling. By default, event handlers are executed in the bubbling phase (unless you set useCapture to true). It goes from the deepest nested element outwards.
33. What's the output?
} console.log(sayHi.call(person, 21)); console.log(sayHi.bind(person, 21));
A: undefined is 21 Lydia is 21
B: function function
C: Lydia is 21 Lydia is 21
D: Lydia is 21 function
const person = { name: 'Lydia' };
function sayHi(age) {
return ${this.name} is ${age}; } console.log(sayHi.call(person, 21)); console.log(sayHi.bind(person, 21));
A: undefined is 21 Lydia is 21
B: function function
C: Lydia is 21 Lydia is 21
D: Lydia is 21 function
DevScrolls
33. What's the output? const person = { name: 'Lydia' }; function sayHi(age) { return ${this.name} is ${age}; } console.log(sayHi.call(person, 21)); console.log(sayHi.bind(person, 21)); A: undefined is 21 Lydia is 21 B: function function C: Lydia is 21 Lydia…
Answer: D
With both, we can pass the object to which we want the this keyword to refer to. However, .call is also executed immediately!
.bind. returns a copy of the function, but with a bound context! It is not executed immediately.
With both, we can pass the object to which we want the this keyword to refer to. However, .call is also executed immediately!
.bind. returns a copy of the function, but with a bound context! It is not executed immediately.
34. What's the output?
function sayHi() {
return (() => 0)();
}
console.log(typeof sayHi());
DevScrolls
34. What's the output? function sayHi() { return (() => 0)(); } console.log(typeof sayHi());
Answer: B
The sayHi function returns the returned value of the immediately invoked function expression (IIFE). This function returned 0, which is type "number".
FYI: typeof can return the following list of values: undefined, boolean, number, bigint, string, symbol, function and object. Note that typeof null returns "object".
The sayHi function returns the returned value of the immediately invoked function expression (IIFE). This function returned 0, which is type "number".
FYI: typeof can return the following list of values: undefined, boolean, number, bigint, string, symbol, function and object. Note that typeof null returns "object".
👏1
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https://thedailyfrontend.com/check-palindrome-with-optimised-solution-in-js/
https://thedailyfrontend.com/check-palindrome-with-optimised-solution-in-js/
The Daily Frontend
Check Palindrome with Optimised Solution in JS - The Daily Frontend
Check palindrome of a given string with an optimised solution. Palindrome is a word or number that reads same as forwards and backwards.
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The frontend blog is about learning skills like HTML, CSS, JavaScript, and frameworks (Angular, React & Vue) & Creating custom UI components.
35. Which of these values are falsy?
A: 0, '', undefined
B: 0, new Number(0), '', new Boolean(false), undefined
C: 0, '', new Boolean(false), undefined
D: All of them are falsy
0;
new Number(0);
('');
(' ');
new Boolean(false); undefined;A: 0, '', undefined
B: 0, new Number(0), '', new Boolean(false), undefined
C: 0, '', new Boolean(false), undefined
D: All of them are falsy
DevScrolls
35. Which of these values are falsy? 0; new Number(0); (''); (' '); new Boolean(false); undefined; A: 0, '', undefined B: 0, new Number(0), '', new Boolean(false), undefined C: 0, '', new Boolean(false), undefined D: All of them are falsy
Answer: A
There are 8 falsy values:
undefined
null
NaN
false
'' (empty string)
0
-0
0n (BigInt(0))
Function constructors, like new Number and new Boolean are truthy.
There are 8 falsy values:
undefined
null
NaN
false
'' (empty string)
0
-0
0n (BigInt(0))
Function constructors, like new Number and new Boolean are truthy.
36. What's the output?
console.log(typeof typeof 1);
console.log(typeof typeof 1);
Anonymous Poll
42%
A: "number"
26%
B: "string"
13%
C: "object"
19%
D: "undefined"
👍1
DevScrolls
36. What's the output?
console.log(typeof typeof 1);
console.log(typeof typeof 1);
Answer: B
typeof 1 returns "number". typeof "number" returns "string"
typeof 1 returns "number". typeof "number" returns "string"
👍1
37. What's the output?
const numbers = [1, 2, 3]; numbers[10] = 11; console.log(numbers);
const numbers = [1, 2, 3]; numbers[10] = 11; console.log(numbers);
Anonymous Poll
29%
A: [1, 2, 3, null x 7, 11]
21%
B: [1, 2, 3, 11]
29%
C: [1, 2, 3, empty x 7, 11]
21%
D: SyntaxError
DevScrolls
37. What's the output?
const numbers = [1, 2, 3]; numbers[10] = 11; console.log(numbers);
const numbers = [1, 2, 3]; numbers[10] = 11; console.log(numbers);
Answer: C
When you set a value to an element in an array that exceeds the length of the array, JavaScript creates something called "empty slots". These actually have the value of undefined, but you will see something like:
[1, 2, 3, empty x 7, 11]
depending on where you run it (it's different for every browser, node, etc.)
When you set a value to an element in an array that exceeds the length of the array, JavaScript creates something called "empty slots". These actually have the value of undefined, but you will see something like:
[1, 2, 3, empty x 7, 11]
depending on where you run it (it's different for every browser, node, etc.)
38. What's the output?
A: 1 undefined 2
B: undefined undefined undefined
C: 1 1 2
D: 1 undefined undefined
(() => {
let x, y;
try {
throw new Error();
} catch (x) {
(x = 1), (y = 2);
console.log(x);
}
console.log(x); console.log(y);
})();A: 1 undefined 2
B: undefined undefined undefined
C: 1 1 2
D: 1 undefined undefined