Question

Consider the following JavaScript skeletal program: //the main program var x: function sub1 () { var x: function sub2 () { } } function sub3 () { } Assume the execution of this program is in the following unit order: main calls sub1 sub1 calls sub2 sub2 calls sub3 a. Assuming static scoping, which declaration of x is the correct one for a reference to x in: i. sub1 ii. sub2 iii. sub3 b. Repeat part a, but assume dynamic scoping Assume the following JavaScript program was interpreted using static-scoping rules. What value of x is displayed in function sub1? Under dynamic scoping rules, what value of x is displayed in function sub1? var x: function sub1() { document.write("x = " + x + " < br/> "): } fuctin sub2 () { var x: x = 10: sub1(): } x = 5: sub2();

Answer 1

var x = 15; // line1

function sub1() {

var x = 16; // line2

  

function sub2() {

sub3();

}

sub2();

}

function sub3() {

}

sub1()

1.

Static Scoping

in Sub1: line2 gives the reference to x

in Sub2: line2 gives the reference to x

in Sub3: line1 gives the reference to x

2.

Dynamic Scoping

in Sub1: line2 gives the reference to x

in Sub2: line2 gives the reference to x

in Sub3: line2 gives the reference to x, because sub2() calls sub3()

Answer2:

var x;

function sub1() {

// as per dynamic scope, sub1 is called from sub2, hence

// the value of x will come from sub2, which is 10

document.write("x = " + x + "<br />");

}

function sub2() {

var x;

x = 10;

sub1();

}

x = 5;

sub2();

1 var x - 15; / line:1 2 function subl) 3 var x 16; // line2 function sub2) 6 sub3 ) sub2 ) 10 function sub3 ) 12 sub1 () 13 14 1. 15 Static Scoping 16 in Subl: line2 gives the reference to x 17 in Sub2: line2 gives the reference to x 18 in Sub3: linel gives the reference to x 19 20 2. 21 Dynamic Scoping 22 in Subl: line2 gives the reference to x 23 in Sub2: line2 gives the reference to x 24 in sub3: line2 gives the reference t x, because sub2() calls sub3() 25 26 27 Answer2: 28 var x; 29 function subl) 30 31 32 // as per dynamic scope, subl is called from sub2, hence // the value of x will come from sub2, which is 10 d cument.write("х- " + x + "<br />"); 34 function sub2 ) 35 36 37 var Xi x 10 subl ); 39 40 x 5; 1 sub2 );