Test your JavaScript Skills:Fundamentals-20

Introduction

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

1. Identify the output of the below program

    if (10-10 || 20-20)
      console.log("true");
    else
      console.log("false");
   

   a.true

   b.false

   c.no output

   d.error

   e.undefined

   Answer: b

   Reason: The computation of both operations yields 0 and 0 is a falsey value.

2. Identify the output of the below program

    let a=20;
    if ((a=a+5) || (a=a+5)) 
      console.log("true", a);
    else
      console.log("false",a);
   

   a.true 30

   b.false 30

   c.true 25

   d.false 25

   e.error

   Answer: c

   Reason: The first conditional expression is true hence the second expression is not evaluated.

3. Identify the output of the below program

    let res = NaN || undefined || 0 || null  ; 
    conseolog("value",res);
   

   a.NaN

   b.undefined

   c.0

   d.null

   e.error

   Answer:d

   Reason: Since none of the values are truthy the last value is taken which is null.

4. Identify the output of the below program

      let b=20;
      if ((b=b-20) || (b=b+5)) 
        console.log("true", b); 
      else
        console.log("false",b);
   

   a.true 0

   b.true 5

   c.false 0

   d.false 5

   e.false 26

   Answer:b

   Reason: The first condition is falsey hence second is evaluated which is true therefore the computation result is 5 which is truthy value.

5. Identify the output of the below program

    if (10-10 || 20-21)
      console.log("true"); 
    else
      console.log("false");
   

   a.false

   b.undefined

   c.error

   d.true

   e.no output

   Answer:d

   Reason: The -1 is a truthy value.

6. Identify the output of the below program

    if (console.log("if"))
          var i=10;
   

   a.if

   b.10

   c.no-output

   d.error

   e.undefined

   Answer: The value 'if' is printed.

   Reason: console.log() is executed.

7. Identify the output of the below program

     if (console.log("if1") && console.log("if2")) 
            var i=10;
     else
            var j=11;
   

   a.if1

   b.if2

   c.if1,if2

   d.error

   e.11

   Answer: a

   Reason: Only 'if1' is printed as the condition is falsey because 1st console.log() returns undefined.