Question

Looping a triangle

You can start with a program that simply prints out the numbers 1 to 7, which you can derive by making a few modifications to the even number printing example given earlier in the chapter, where the for loop was introduced.

Now consider the equivalence between numbers and strings of hash characters. You can go from 1 to 2 by adding 1 ( += 1 ). You can go from "#" to "##" by adding a character ( += "#" ). Thus, your solution can closely follow the number-printing program.

FizzBuzz

Going over the numbers is clearly a looping job, and selecting what to print is a matter of conditional execution. Remember the trick of using the remainder ( % ) operator for checking whether a number is divisible by another number (has a remainder of zero).

In the first version, there are three possible outcomes for every number, so you’ll have to create an if / else if / else chain.

The second version of the program has a straightforward solution and a clever one. The simple way is to add another “branch” to precisely test the given condition. For the clever method, build up a string containing the word or words to output, and print either this word or the number if there is no word, potentially by making elegant use of the || operator.

Chess board

The string can be built by starting with an empty one ( "" ) and repeatedly adding characters. A newline character is written "\n" .

Use console.log to inspect the output of your program.

To work with two dimensions, you will need a loop inside of a loop. Put curly braces around the bodies of both loops to make it easy to see where they start and end. Try to properly indent these bodies. The order of the loops must follow the order in which we build up the string (line by line, left to right, top to bottom). So the outer loop handles the lines and the inner loop handles the characters on a line.

You’ll need two variables to track your progress. To know whether to put a space or a hash sign at a given position, you could test whether the sum of the two counters is even ( % 2 ).

Terminating a line by adding a newline character happens after the line has been built up, so do this after the inner loop but inside of the outer loop.

This is a book about getting computers to do what you want them to do. Computers are about as common as screwdrivers today, but they contain a lot more hidden complexity and thus are harder to operate and understand. To many, they remain alien, slightly threatening things.