Theory
Theory
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Managing the number of copies

The driver can make three copies of the given page. Now you need to train it to make a different number of copies depending on the situation. You already know how conditions work, and that’s why you could write the program like this:

// Variable stores the necessary number of copies
var count = 3;

if (count === 2) {
  muffin.print(page);
  muffin.print(page);
}

if (count === 3) {
  muffin.print(page);
  muffin.print(page);
  muffin.print(page);
}

In general, the approach is working, but no one writes programs like that. Imagine a program that can make one hundred copies of one page.

Programming languages provide loops to repeat commands conveniently. Here’s a for loop:

for (var i = 0; i < count; i = i + 1) {
  // repeated commands
}

In this for loop, the commands inside the curly braces run count times. We’ll examine the parts inside the parentheses in the next task. For now, let’s try it out.

Modify the driver so that you can control the number of copies with the variable count.

By the way, in the “Conditions” chapter, we looked at strict (===) and loose (==) equality. Why does the example above use strict equality?

Strict equality helps prevent errors. For example, this condition is true when we use loose equality:

if ('003' == 3) {
  // …
}

The same condition using === is false, because the string '003' is not the same as the number 3. Our program stores the copy count as a number and expects a number in each comparison. Strict equality prevents values of other types from being treated as equal.

Using strict equality is good practice. Use it and nothing else in all cases where possible.

script.js

JavaScript

var page = 7; var count = 3; muffin.print(page); muffin.print(page); muffin.print(page);

Goalscompleted

Replace command duplication with the for loop.

Delete the muffin.print commands and replace them with the loop: for (var i = 0; i < count; i = i + 1) { }.
Inside the loop, add the command muffin.print(page).
Change the value of the variable count to 5 and make sure that the number of printed copies has changed.

Managing the number of copies

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Result

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