Question

List the five implementation models of parameter passing.

Consider the following closure in JavaScript:

1- function makeAdder(x) {

2- return function(y) {return x + y;}

3- } . . .

4- var add1 = makeAdder(0);

5- var add2 = makeAdder(10);

6- document.write(add1(20));

7- document.write(add2(20));

Questions:

a) Show the output.

b) What is the closure subprogram in this example?

c) Explain how the variable x referenced at line 2 is bound.

Answer 1

In case of any query do comment. Please rate answer. Thanks

Answer a: 20 30

Explanation: makeAdder(x) is taking one parameter as x and return a new function which takes another parameter as y

and then return the x+y. so when on line 4 you created add1 = makeAdder(0) (which is closure in Java script), which is in turn returning a function with value of x as 0 so when called in line 6 as add1(20) i.e. x is 0 here and y is 20 here so the result would be 0 + 20 =20

in the same way when on line 5 you created add2 = = makeAdder(10) (which is closure in Java script), which is in turn returning a new function with value of x as 10 so when called in line 7 as add2(20) i.e. x is 10 here and y is 20 here so the result would be 10 + 20 =30

Answer b: add1 and add2 are both closure subprograms.

Explanation: Whenever we are using makeAdder() to create a new subprogram, it will be a closure subprogram which shares same definition.

Answer c: As I also explained in answer a, Closure is javscript construct which allows lexical scoping. It means you can access a variable from outer function inside the inner function. so basically makeAdder is returning a function with two variable one is from outer scope as x and another one from inner scope as y and returning the result as x+y