Test Your JavaScript Skills : ES12 (JavaScript 2021) - 38

Introduction

Namaste, In this blog I will discuss 10 code scenarios on Javascript .

1. Identify the output of the below program

    let str = "Namaste Java";
    let str2 = str.replaceAll("Java", "Javascript");
    console.log(str2);
   

   a.Namaste Java

   b.Namaste Javascript

   c.undefined

   d.null

   e.error

   Answer:b

   Reason:The string Java is replaced by Javascript.

2. Identify the output of the below program

    let a=true;
    a &&= false;
    console.log(a);
   

   a.true

   b.undefined

   c.null

   d.false

   e.error

   Answer:d

   Reason:The logical and assignment operator evaluates to false in the above scenario.

3. Identify the output of the below program

    let num= 1_0_0_0;
    console.log(num);
   

   a.1

   b.10

   c.1000

   d.100

   e.error

   Answer:c

   Reason:Numeric separator enhances code readability.

4. Identify the output of the below program

    let a=false;
    a ||= true;
    console.log(a);
   

   a.false

   b.true

   c.undefined

   d.error

   e.null

   Answer:b

   Reason:The expression evaluates to true.

5. Identify the output of the below program

    let a=true;
    a ||= false;
    console.log(a);
   

   a.true

   b.false

   c.undefined

   d.null

   e.error

   Answer:a

   Reason:The expression evaluates to true.

6. Identify the output of the below program

    let a=false;
    a &&= false;
    console.log(a);
   

   a.true

   b.false

   c.error

   d.undefined

   e.error

   Answer:b

   Reason:The expression evaluates to false.

7. Identify the output of the below program

    let str = "Java Java";
    console.log(str.replaceAll("Java", "Javascript"));
   

   a.Javascript Javascript

   b.Java Java

   c.Javascript

   d.Java

   e.error

   Answer: a

   Reason: The string Java is replaced by Javascript at all places.

8. Identify the output of the below program

    let x;
    let y = 10;
    x ??= y;
    console.log(x);
   

   a.undefined

   b.null

   c.10

   d.true

   e.false

   Answer:c

   Reason:Since x is undefined value 10 is assigned to it.

9. Identify the output of the below program

    let x=2;
    let y = 10;
    x ??= y;
    console.log(x);
   

   a.2

   b.10

   c.false

   d.true

   e.error

   Answer:a

   Reason:Since x is already initialized the value of y is not initialized.

10. Identify the output of the below program

    let str = "Namaste Java";
    let str2 = str.replaceAll("Java", "Javascript");
    console.log(str);
    

    a.Namaste Java

    b.Namaste Javascript

    c.error

    d.null

    e.undefined

    Answer:a

    Reason:The host string is not updated by replaceAll() function.