Java Reference
In-Depth Information
The block of code uses the alert function to display a message about the number of
bottles, and then uses the decrement operator to decrease the bottles variable by one.
Here's a more concise way of writing the same loop that moves the increment into the con-
var bottles = 11;
while (--bottles){
alert("There were " + bottles + " green bottles, hanging
on the
wall. And if one green bottle should accidently fall,
there'd be
" + (bottles-1) + " green bottles hanging on the wall");
The reason that this code works is because the loop will continue while the bottles vari-
able is true, and after each loop, the value of the bottles variable decreases by 1 . When
the bottles variable reaches 0 , it is not true anymore (remember that 0 is a falsy value)
so the loop will stop. Notice that you have to start with one more bottle (11) as it will be
decreased by one even before the first block is run.
Infinite Loops
It is important that the condition in a while loop will be met at some point, otherwise
you'll be stuck in an infinite loop that can crash your program.
Consider the following loop:
var n = 1;
This loop will keep running, as the variable n will always be above zero. Most browsers
will warn you that there is a slow running script when this happens and give you the option
to stop it. If not, you can usually kill the process by closing the tab or restarting the browser.
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