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1. What is the difference between var, let, and const in JavaScript?
Anonymous Quiz
8%
A)var is block-scoped, let is function-scoped, and const can be re-assigned.
83%
B)var is function-scoped, let is block-scoped, and const is constant and cannot be re-assigned.
0%
C)var and let are the same, but const is used only for objects.
8%
D)var, let, and const are all the same in terms of scope.
2. What will the following code log to the console?console.log(2 + '2');
Anonymous Quiz
69%
A) 22
15%
B) 4
8%
C) undefined
8%
D) Error
3. What does === do in JavaScript?
Anonymous Quiz
8%
A) Compares only values, ignoring the type.
67%
B) Compares both value and type
0%
C) Assigns values to variables.
25%
D) Returns a boolean indicating if two values are equal.
let a = 10;
function foo() {
a = 20; console.log(a); } foo(); console.log(a);
function foo() {
a = 20; console.log(a); } foo(); console.log(a);
Anonymous Quiz
22%
A) 10 and 10
56%
B) 20 and 10
22%
C) 20 and 20
0%
D) Error
5. What is a JavaScript closure?
Anonymous Quiz
0%
A) A function that defines a loop.
100%
B) A function that returns another function and retains access to the outer function’s variables.
0%
C) A function that is used to close open tabs in a browser.
0%
D) A JavaScript method that allows for asynchronous operations.
6. What is null vs. undefined in JavaScript?
Anonymous Quiz
14%
A) null means an object, and undefined means no value.
14%
B) null is a variable that has not been initialized, and undefined is the absence of a value.
71%
C) null represents no value, and undefined means a variable is declared but not yet assigned.
0%
D) null and undefined are the same.
7. What will the following code output? const arr = [1, 2, 3];
arr[10] = 5;
console.log(arr);
arr[10] = 5;
console.log(arr);
Anonymous Quiz
14%
A) [1, 2, 3, 5]
57%
B) [1, 2, 3, <7 empty items>, 5]
14%
C) [1, 2, 3, 5, undefined]
14%
D) [1, 2, 3, undefined, 5]
8. How can you create a new object in JavaScript?
Anonymous Quiz
14%
A) let person = Object.create(null);
14%
B) let person = new Object();
43%
C) let person = { name: 'Alice', age: 25 };
29%
D) All of the above
9. What is the output of the following code? console.log(typeof NaN);
Anonymous Quiz
18%
A) object
27%
B) undefined
45%
C) number
9%
D) NaN
10. What is the purpose of the this keyword in JavaScript?
Anonymous Quiz
71%
A) Refers to the current function's parameters.
29%
B) Refers to the object in which the function was called.
0%
C) Refers to the global object, regardless of the context.
0%
D) Refers to the last variable declared in the script.
🎉 : Spread the Love! Cloning Arrays Made Easy 🌟
Want to create a quick copy of an array? Use the spread operator (...)! It's super simple:
const originalArray = [1, 2, 3];
const clonedArray = [...originalArray];
console.log(clonedArray); // Output: [1, 2, 3]
✨ Pro Tip: This creates a shallow copy, so the clonedArray is a fresh array, but if your original array has nested objects, they will still be linked! Keep that in mind for deep copies. 😉
#JavaScript #CodingTricks #SpreadOperator
What is a void operator? The void operator returns an undefined value from an evaluated expression, or in other words; the void operator specifies an expression to be evaluated without returning a value. It is commonly used in client-side JavaScript, where the browser should not display the value.
function getYear() {
return 2020;
};
console.log(getYear());
// Output: 2020
console.log(void getYear());
// Output: undefined
// Useful use case
button.onclick = () => void getYear();The World’s First Web Site
On August 6, 1991, without fanfare, British computer scientist Tim Berners-Lee published the first-ever website while working at CERN, the huge particle physics lab in Switzerland. https://info.cern.ch/hypertext/WWW/TheProject.html
On August 6, 1991, without fanfare, British computer scientist Tim Berners-Lee published the first-ever website while working at CERN, the huge particle physics lab in Switzerland. https://info.cern.ch/hypertext/WWW/TheProject.html