Test your JavaScript Skills:Fundamentals-10

Introduction

Namaste, In this blog I will discuss 7 code scenarios on Javascript fundamentals.

1. Identify the output of the below program

    if (NaN+1)
        console.log("true");
    else
       console.log("false");
   

   a.false

   b.true

   c.error

   d. undefined

   e.NaN

   Answer: a

   Reason: NaN+1 is NaN which is a falsey value hence result is false.

2. Identify the output of the below program

    if (-Infinity)   
      console.log("true");
    else
      console.log("false");
   

   a.error

   b.undefined

   c.true

   d. false

   e.-Infinity

   Answer:c

   Reason: -Infinity is a truthy value.

3. Identify the output of the below program

    if(null+1)  
        console.log("true");
    else
      console.log("false");
   

   a.error

   b.NaN

   c.false

   d. true

   e.undefined

   Answer: d

   Reason: The null is coerced into a number which is 0 hence (0 + 1) is 1, which is a truthy value.

4. Identify the output of the below program

    if ({})  
       console.log("true"); 
    else
      console.log("false");
   

   a.undefined

   b.null

   c.true

   d.error

   e.false

   Answer: c

   Reason: An empty object is a truthy value.

5. Identify the output of the below program

    if(undefined+1)  
        console.log("true"); 
    else
      console.log("false");
   

   a.true

   b.false

   c.error

   d. undefined

   e.1

   Answer: b

   Reason: The undefined is coerced into a number which is NaN and NaN + 1 is NaN which is falsey.

6. Identify the output of the below program

    if (Infinity)   
      console.log("true"); 
    else
      console.log("false");
   

   a.true

   b.false

   c.error

   d.undefined

   e.Infinity

   Answer: a

   Reason: Infinity is a number that is non-zero and it is considered to be a truthy value.

7. Identify the output of the below program

    if ([])  
      console.log("true"); 
    else
      console.log("false");
   

   a. true

   b.error

   c.false

   d. undefined

   e.0

   Answer: a

   Reason: An empty array is an object that is a truthy value.