While Loops

The first 3 lines are a function that uses a random number generator. randomNumber() gives a value between 0 and 1, but never including 1 (between 0 and .99999). The floor makes it round down and the + 1 ensure that you never get a 0 back. the upper is the top number that the function will return.

The loop starts by declairing the variable counter and setting it to 0. Line 6 starts the loop with while and a test condition in parentheses which will run untill it tests false. In this case it is checking the counter var to see if it is less than 10. 0 < 10 so the loop will continue. line 7 creates a new variable named rand and sets the function equal to it. the 9 is the upper limit. line 8 does the purpose of the loop, in this case it writes the random number generated to the document. Finally line 9 adds the the counter variable and starts the loop over again. At this point the loop tests the condition again ( now 1 < 10 ) and continues again until the test condition is false (on the 10th pass 10 !< 10) so the loop is finished.

If this loops test condition is false, it will never run at all, and if it always tests right it is a infinite loop.

Do {} while () Loop

These loops are very similar to while loops, the main difference is that this loop always runs the first time because the loop is ran before the test condition is tested. This loop is useful to prompt a user to give you information and make sure that they give you it to you by repeatedly prompting them. Usually use a true false variable as a flag to see if the condition was met.

This example starts by setting up the variables, and the standard RandomNumber generator. The formatting of the loop is different...The loop is presented first, and then the test condition is afterward in the while elemenet. In this case the test condition is that the correctGuess is wrong. So until you guess correctly, the game will continue, but it always runs atleast once.

For Loop

The entire first time is the counter info, line 2 is the loop itself and the 3rd line is the close. It’s common to set the counter variable as a single letter (i).

This example shows a couple of important ideas of loops. The for loop is very similar to while and do while, but it is more condensed. And this particular loops shows how you can use it to create html, and insert things into a website. This example produces 25 randomly colored boxes.