Quiz: JavaScript Arrays

Here is a bunch of questions related to JavaScript arrays. It helps a developer to test his/her knowledge about JavaScript arrays.

Question 1:

Which of the following is / are valid statement(s) to declare an array?

A. const arr = [2, 4, 6];

B. const arr = new Array(2, 4, 6);

C. const arr = Array(2, 4, 6);

A and B

Only A

B and C

A, B and C

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Question 2:

What is the output?

const arr = [2,,,4,];
console.log(arr.length);

5

4

2

SyntaxError: Invalid operator ,

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Question 3:

What is the output?

const arr = [,,,];
console.log(arr.length);

3

2

4

1

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Question 4:

What is the output?

const arr = Array(3);
console.log(arr);

undefined

[3]

[undefined, undefined, undefined]

None of these

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Question 5:

What is the output?

const arr = ["Mercedes", "BMW", "Audi"];
console.log(arr[1]);

"BMW"

"Mercedes"

"Audi"

undefined

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Question 6:

What is the output?

const arr = ["Mercedes", "BMW", "Porsche"];
console.log(arr[1000]);

undefined

ReferenceError: Array out of bound exception

null

""

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Question 7:

What is the output?

const arr = ["Apple", "Banana", "Orange"];
console.log(arr["2"]);

undefined

"Orange"

TypeError: Invalid array index

"Banana"

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Question 8:

In what all ways, we can check if a variable arr contains an array in JavaScript?

A. Array.isArray(arr) === true

B. arr.constructor.name === "Array"

C. typeof arr === "Array"

A and B

Only A

B and C

A, B and C

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Question 9:

What is the output?

const arr1 = [1, 3, 5];
const arr2 = [2, 4, 6];
arr1.concat(arr2);
console.log(arr1);

[1, 2, 3, 4, 5, 6]

[2, 4, 6]

[1, 3, 5, 2, 4, 6]

[1, 3, 5]

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Question 10:

const arr1 = ["Apple", "Banana"];
const arr2 = arr1.concat();
arr2[0] = "Pineapple";
console.log(arr1);

["Apple", "Banana"]

["Pineapple", "Banana"]

SyntaxError: missing argument for concat()

["Apple", "Banana", "Pineapple"]

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Question 11:

What is the output?

const arr = [2, 4, 6];
const result = arr.every(ele => ele * 2);
console.log(result);

true

[4, 8, 12]

false

[2, 4, 6]

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Question 12:

What is the output?

const arr = [1, 3, 5, 7];
console.log(arr.fill(6, 1, 3));

[1, 6, 6, 7]

[1, 6, 6, 6]

[6, 1, 3, 7]

[6, 1, 3, 6]