# 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**
    
    ```javascript
    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**
    
    ```javascript
    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**
    
    ```javascript
    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**
    
    ```javascript
    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**
    
    ```javascript
    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**
    
    ```javascript
    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**
    
    ```javascript
    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**
    
    ```javascript
    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.**