Test your JavaScript Skills : Double not operator

Introduction

Namaste, In this blog I will discuss 10 code scenarios on double not operator.

1. Identify the output of the below program

    let v = !!10;
    console.log(v);
   

   a. true

   b. false

   c. 10

   d. undefined

   e. null

   Answer: a

   Reason: The double not operator for a non-zero number is true

2. Identify the output of the below program

    let v = !!"JS";
    console.log(v);
   

   a.false

   b.JS

   c.undefined

   d.null

   e.true

   Answer:e

   Reason: The double not operator for a non-empty string is true

3. Identify the output of the below program

    let v = !!"  ";
    console.log(v);
   

   a.true

   b.false

   c.undefined

   d.null

   e.error

   Answer: a

   Reason: The double not operator for a non-empty (even spaces) string is true

4. Identify the output of the below program

    let v = !!"";
    console.log(v);
   

   a.false

   b.true

   c.undefined

   d.null

   e.error

   Answer: a

   Reason: The double not operator for an empty string is false

5. Identify the output of the below program

    let v = !!null;
    console.log(v);
   

   a.null

   b.undefined

   c.true

   d.false

   e.error

   Answer:d

   Reason: The double not operator for null is false

6. Identify the output of the below program

    let v = !!NaN;
    console.log(v);
   

   a.undefined

   b.NaN

   c.true

   d.false

   e.error

   Answer:d

   Reason: The double not operator for NaN is false

7. Identify the output of the below program

    let v = !!Infinity;
    console.log(v);
   

   a.false

   b.true

   c.Infinity

   d.null

   e.error

   Answer: b

   Reason: The double not operator for Infinity is true

8. Identify the output of the below program

    let v = !!-Infinity;
    console.log(v);
   

   a.false

   b.true

   c.Infinity

   d.null

   e.error

   Answer: b

   Reason: The double not operator for -Infinity is true

9. Identify the output of the below program

    let v = !!0;
    console.log(v);
   

   a.false

   b.true

   c.Infinity

   d.null

   e.error

   Answer: a

   Reason: The double not operator for 0 is false

10. Identify the output of the below program

    let v = !!{};
    console.log(v);
    

    a.false

    b.true

    c.Infinity

    d.null

    e.error

    Answer: b

    Reason: The double not operator for the empty object is true