Test Your JavaScript Skills : ES10 (JavaScript 2019) - 42

Introduction

Namaste, In this blog I will discuss 8 code scenarios on Javascript .

1. Identify the output of the below program

    let nestedArray = [1, [2, [3]]];
    const flattened = nestedArray.flat(2);
    console.log(flattened);
   

   a. Object

   b.[1, [2, [3]]]

   c.[1, 2, 3]

   d.[1, [2, 3]]

   e.2

   Answer:c

   Reason:The flat() function returns a new array flattened at depth 2.

2. Identify the output of the below program

    let myArr = [[1, 2], [3, 4], [5, 6]];
    let newArr = myArr.flat();
    console.log(newArr);
   

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

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

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

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

   e.Object

   Answer:b

   Reason:The host array returns an array flattened at level 1 by default.

3. Identify the output of the below program

    let myArr = [1, 2, 3, 4, 5, 6];
    let newArr = myArr.flatMap((x) => x * 2);
    console.log(newArr);
   

   a.[2, 4, 6, 8, 10, 12]

   b.[2, 4, 6, 8]

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

   d.[12,10,8,6,4,2]

   e.Object

   Answer:a

   Reason:The callback function returns a new updated array.

4. Identify the output of the below program

    let myArr = [[1], [2], [3]];
    let newArr = myArr.flat();
    console.log(newArr);
   

   a.[[1], [2], [3]]

   b.[1], [2], [3]

   c.[[1], [2], [3]]

   d.[[1,2,3]]

   e.[1,2,3]

   Answer:e

   Reason:The host array is flattened at level 1 and a new array is returned.

5. Identify the output of the below program

    try {
        throw 10;
    }catch {
        console.log("error");
    }
   

   a.10

   b.error

   c.no output

   d.object

   e.1

   Answer:b

   Reason:The error raised is caught by catch where error is printed.

6. Identify the output of the below program

    try {
        a=20;
    }catch {
        console.log("error");
    }
   

   a.20

   b.Object

   c.error

   d.undefined

   e.no output

   Answer:c

   Reason:The variable is not created hence caught by catch.

7. Identify the output of the below program

    let nestedArray = [1, [2, [3]]];
    const flattened = nestedArray.flat(1);
    console.log(flattened);
   

   a.[1, [2, [3]]]

   b.[1, 2, 3]

   c.[1, [2, 3]]

   d.[1, 2, [3]]

   e.error

   Answer:d

   Reason:The array is flattened at depth 1 and returns a new array.

8. Identify the output of the below program

    let myArr = [1, 2, 3, 4, 5, 6];
    let newArr = myArr.flatMap((x) => x +1 );
    console.log(newArr);
   

   a.[2,3,4,5,6,7]

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

   c.[2, 4, 6, 8, 10, 12]

   d.Object

   e.[1,2]

   Answer:a

   Reason:The callback function increments each value by 1 and returns a new array.