Test your JavaScript Skills:Fundamentals-21

Introduction

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

1. Identify the output of the below program

    let res = NaN || undefined || 0; 
    console.log("value",res);
   

   a.NaN

   b.undefined

   c.0

   d.no output

   e.error

   Answer: c

   Reason: All are falsey values hence the last value is taken which is 0.

2. Identify the output of the below program

    let res = 10 && 20 && 30 && 40;
    console.log("res", res);
   

   a.10

   b.20

   c.30

   d.40

   e.error

   Answer:d

   Reason: The last value is taken as all values are truthy.

3. Identify the output of the below program

    let res = !undefined;
    console.log("res", res);
   

   a.undefined

   b.error

   c.false

   d.true

   e.no output

   Answer:d

   Reason:The not of undefined is true because undefined is falsey value.

4. Identify the output of the below program

    let res = NaN || undefined || -1 || null; 
    console.log("value", res);
   

   a.NaN

   b.null

   c.undefined

   d.-1

   e.error

   Answer: d

   Reason: The first truthy value is taken which is -1.

5. Identify the output of the below program

    undefined || false || null || console.log("Namaste");
   

   a. false

   b.null

   c.Namaste

   d.undefined

   e.error

   Answer: c

   Reason: All are falsey values hence last instruction is executed which prints Namaste.

6. Identify the output of the below program

    let res = null && undefined && NaN;
    console.log("value", res);
   

   a.NaN

   b.undefined

   c.null

   d.error

   e.no output

   Answer:c

   Reason: The first falsey value is taken hence the output is null.

7. Identify the output of the below program

    undefined || false || -2 || console.log("Namaste");
   

   a. no output

   b. Namaste

   c.undefined

   d.false

   e.-2

   Answer: a

   Reason: The value -2 is truthy (taken) but it is not printed.