Test your JavaScript Skills:Fundamentals-1

Introduction

Namaste, In this blog post I will discuss 7 common FAQs on JS Fundamentals

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1. Identify the output of the below program

    let mydata = "data" / 2;
    console.log("mydata", mydata);
   

   a. Error

   b. data

   c. undefined

   d. NaN

   Answer: d

   Reason: The string is coerced into a number which is NaN and the division of NaN is NaN.

2. Identify the output of the below program

    let mydata = "data" / 2;
    console.log("type", typeof mydata);
   

   a. number

   b. string

   c. undefined

   d. Error

   Answer: a

   Reason: NaN is a number type

3. Identify the output of the below program

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

   a. 1

   b. 0

   c. Infinity

   d. Error

   Answer: c

   Reason: The true is coerced to 1 and the false to 0. Hence the division of 1/0 is

   Infinity in Javascript.

4. Identify the output of the below program

    console.log(typeof boolean, typeof  number, typeof string);
   

   a. boolean, number, string

   b. null, null, null

   c. Error

   d. undefined, undefined, undefined

   Answer: d

   Reason: The boolean, number and string are not primitives. They are also not declared and hence undefined for all.

5. Identify the output of the below program

    console.log(typeof Infinity, typeof NaN);
   

   a. Error

   b. number, number

   c. undefined, undefined

   d. null, null

   Answer: b

   Reason: Infinity and NaN are number types.

6. Identify the output of the below program

    let mydata= 100n
    console.log(typeof mydata, mydata);
   

   a. number, 100

   b. string, 100n

   c. bigint, 100n

   d. Error

   Answer: c

   Reason: Integer values suffixed with n is identified as bigint.

7. Identify the output of the below program

    console.log(typeof typeof);
   

   a. number

   b. string

   c. undefined

   d. Error

   Answer: d

   Reason: Since typeof is an operator and the operand passed to it is also typeof, it is considered an invalid operand (because is it pre-defined).

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