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Arrays
Question 1
What is the index of the first element in a JavaScript array?
- A
1
- B
0
- C
-1
- D
undefined
Question 2
What is the output of the following code?
let a = [10, 20, 30];
console.log(a[1]);
- A
10
- B
20
- C
30
- D
undefined
Question 3
Which method is used to add an element to the beginning of an array?
- A
push()
- B
pop()
- C
unshift()
- D
shift()
Question 4
What does the following code do?
let a = [1, 2, 3];
a.length = 2;
console.log(a);
- A
[1, 2]
- B
[2, 3]
- C
[1, 2, 3]
- D
[1, 2, 3,
]
Question 5
Which of the following methods modifies the original array?
- A
concat()
- B
slice()
- C
reverse()
- D
toString()
Question 6
What will be the output of the following code?
let a = [10, 20, 30];
console.log(a.pop());
- A
30
- B
10
- C
Undefined
- D
Error
Question 7
How do you check if a variable a is an array?
- A
typeof a === 'array'
- B
Array.isArray(a)
- C
a instanceof Object
- D
a.constructor === Array
Question 8
What does the splice() method do?
- A
Adds elements to the end
- B
Removes elements from the array
- C
Adds and removes elements
- D
Merges two arrays
Question 9
What is the result of the following code?
console.log([] + []);
- A
NaN
- B
""
- C
[]
- D
undefined
Question 10
What does a closure in JavaScript do?
- A
Accesses outer function variables
- B
Only accesses global variables
- C
Is not useful in async code
- D
Can't access outer variables
There are 10 questions to complete.