Test your JavaScript Skills: Fundamentals-3

Introduction

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

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1. Identify the output of the below program

    let mydata = null +1;
    console.log("mydata", mydata);
   

   a.error

   b.null

   c.undefined

   d.1

   e.2

   Answer:d

   Reason: The null is coerced to a number which is 0 hence 0+1 is 1.

2. Identify the output of the below program

    let mydata="ram" + 2;
    console.log("mydata", mydata);
   

   a.NaN

   b.ram2

   c.error

   d. undefined2

   e.null

   Answer:b

   Reason: When the + operator is used with a string it performs concatenation. Hence 2 is coerced to a string.

3. Identify the output of the below program

    let mydata=true/false;
    console.log("mydata", mydata);
   

   a.1

   b.0

   c.error

   d. Infinity

   e.undefined

   Answer:d

   Reason: Here true is coerced into 1 and false to 0 hence 1/0 is Infinity in Javascript.

4. Identify the output of the below program

    let mydata= null+undefined;
    console.log("mydata", mydata);
   

   a.error

   b.0

   c.NaN

   d. nullundefined

   e.undefined

   Answer:c

   Reason: Here null is coerced into 0 and undefined to NaN. Hence 0 + NaN is NaN.

5. Identify the output of the below program

    let mydata = false/true;
    console.log("mydata", mydata);
   

   a.0

   b.1

   c.NaN

   d. Infinity

   e.error

   Answer: a

   Reason: Here false is coerced into 0 and true into 1 hence 0/1 in Javascript is 0.

6. Identify the output of the below program

    let mydata = true + 1;
    console.log("mydata", mydata);
   

   a.1

   b.true

   c.2

   d. NaN

   e.true1

   Answer:c

   Reason: Here true is coerced to a number which results in 1 hence 1+1 is 2.

7. Identify the output of the below program

    let mydata = undefined + 1;
    console.log("mydata", mydata);
   

   a.undefined

   b.undefined1

   c.1

   d. error

   e.NaN

   Answer:e

   Reason: The undefined is coerced to a number which results in NaN hence NaN+1 is NaN.

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