Test your JavaScript Skills:Fundamentals-6

Introduction

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

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1. Identify the output of the below program

    var i=100;
    var i=20;
    console.log("value", i);
   

   a.20

   b.100

   c.error

   d. 120

   e.undefined

   Answer: a

   Reason: The 'var' allows the redeclaration of a variable.

2. Identify the output of the below program

    console.log("value", myval);
    var myval=20;
   

   a.20

   b.error

   c.undefined

   d. null

   e.0

   Answer: c

   Reason: Since 'var' performs hoisting the value is undefined.

3. Identify the output of the below program

    function fx() {
     console.log("value", myval);
    }
    fx();
    var myval=10;
   

   a.undefined

   b.20

   c.error

   d. null

   e.0

   Answer: a

   Reason: Since 'var' performs hoisting the value is undefined.

4. Identify the output of the below program

    function fx() {
        console.log("value", myval+myval2);
       }
       fx();
       var myval=10;
       var myval2=20;
   

   a.error

   b.30

   c.undefined

   d. NaN

   e.null

   Answer: d

   Reason: After hoisting the value undefined is coerced to a number which results in NaN hence NaN+NaN is NaN.

5. Identify the output of the below program

    var j=20;
    if (j > 3) {
     var i=3;
    }
    console.log("value", i);
   

   a.20

   b.3

   c.undefined

   d. error

   e.NaN

   Answer: b

   Reason: Since the 'var' declaration does not have a block scope variable can be accessed outside the block.

6. Identify the output of the below program

    var j=20;
    if (j > 3) {
     var i=3;
    }
   
    function fx() {
        console.log("value", i);
    }
       fx();
   

   a.20

   b.undefined

   c.3

   d. error

   e.NaN

   Answer: c

   Reason: Since the 'var' declaration does not have a block scope variable can be accessed outside the block.

7. Identify the output of the below program

    for (var i=0; i< 4;) {
        i++;
    }
   
    console.log("value", i);
   

   a.null

   b.undefined

   c.NaN

   d. 3

   e.4

   Answer: e

   Reason: Since the 'var' declaration does not have a block scope variable can be accessed outside the block.

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