Challenge From Last Time:
Somehow you find yourself in a room with 2 identical doors. One will lead you into an endless maze that will surely result in your death, the other will take you to freedom and happiness. You must choose one of the doors eventually because if you stay in the room, you will starve to death. In the room there are 2 identical talking birds, one always lies the other always tells the truth. You may ask only one of the birds only one simple question. This cannot be a complex sentence with lots of conjunctions. Will you ever get out of the room? If so, what question should you ask? If not, then why?
Functions Я us
Answer the last challenge question or tell me something you know
about strings in JavaScirpt to get a sandwich.
JavaScript is often used for form validation. That is, it's used to
make sure that the input given by a user in the form is syntactically
correct. Today we're going to write a couple of functions that could
be used for form validation. Split up into groups of 3 and write the
following functions. What do you think each of these functions could
be used for?
- Write a function that takes in a string and outputs the
content of that string with all spaces, dashes, parenthesis, and
periods removed.
function cleanUp(str) { ... return cleanStr; }
- Write a function that takes in a string and outputs the
contents of the string with all leading and trailing spaces
removed.
function trim(str) { ... return trimmedStr; }
- Write a function that takes in a string and outputs whether or
not the string has one occurrence of an '@' (at sign) and at
least one '.' (period), such that a period exists in the string
sometime after the '@' sign.
function isValid(str) { ... return true; ... return false; }
A Challenge For Next Time:
A group of people live on an island. They are all perfect logicians.
No one knows the color of their eyes. Every night at midnight, a
ferry stops at the island. If anyone has figured out the color of
their own eyes, they [must] leave the island that midnight. On this
island live 100 blue-eyed people, 100 brown-eyed people, and the
Guru. The Guru has green eyes, and does not know her own eye color
either. Everyone on the island knows the rules (but are not given the
total numbers) and is constantly aware of everyone else's eye
color. Everyone keeps a constant count of the total number they see
of each (excluding themselves). However, they cannot otherwise
communicate. So any given blue-eyed person can see 100 people with
brown eyes and 99 people with blue eyes, but that does not tell them
their own eye color; it could be 101 brown and 99 blue. Or 100 brown,
99 blue, and the one could have red eyes.
The Guru speaks only once (let's say at noon), on one day in all
their endless years on the island. Standing before the islanders, she
says the following:
"I can see someone with blue eyes."
Who leaves the island, and on what night?