page that you can read into an active, dynamic application you
can interact with, such as Gmail, Facebook, and many more.
Consequently, it's difficult. Any first programming
language is, but all programming languages bear many
similarities, so learning part of one will help you immensely in
learning your second.
We won't become experts in JS, but we'll learn a lot of the
fundamental ideas behind all programming languages, such as:
var price = 5.99;
var x = 100;
var total_price = (price - discount) * (1 + tax_rate);
var item_name = "Fizzing Whizbee";
var z = (3*x+1)/2;
var y = (x+5)%7;
var fname = "Harry";
var lname = 'Potter';
var name2 = "O'Malley"; // can't use single quotes here
var quote = "Hermione said, 'Wingardium LeviOsa'"; // need double quotes here
var fname = "Harry";
var lname = "Potter";
var whole_name = fname + lname;
alert("Butterbeer costs ");
console.log("Madame Rosmerta waters the butterbeer");
var pass = prompt("what is the password for Gryffindor tower?");
var pass = prompt("what is the password for Gryffindor?","caput draconis");
var how_many = prompt("how many butterbeers?");
var n = parseInt(how_many);
var price = prompt("what price?","8.99");
inline, using special tag attributes
in the document, using the <script> tag
in an external file, using the <script> tag
all of the above
double slashes like this: // tricky
slash star like this: /* tricky */ tag
/* tricky */
angle brackets like this: <!-- tricky --> tag
<!-- tricky -->
none of the above
What's wrong with the following code?
5.99 x 1.62 = price-with-tax
assignment in the wrong order
variable name has wrong syntax
incorrect operator used
var long_quote = "Now is the winter of our discontent
made glorious summer by this son of York";
Wrong quotation marks
underscore in variable name is incorrect
line break in string literal is not allowed.
nothing; the code is fine
Explain the following code. Predict what it will do if someone types in 18.
var age = prompt("Enter your age ");
var next = age + 1;
alert("On your next birthday, you'll be "+next);
It gets an error
It displays "18"
It displays "19"
It displays "181"
Now, run the code. Explain its behavior.
The plus sign means addition
The plus sign means concatenation
The code does the wrong thing
The code stores something in the variable age, then creates a
variable next and assigns in age+1, then
does an alert with a string and the variable next
see error messages and even type in code to try. Let's do that together.
some number of years after we buy it. We buy it as a sapling that is 6
feet high, and the nursery predicts that the tree will grow 2 feet per
year. This is a situation where we can use the y = mx + b
linear functions we learned in high school. For example, if the user
wants to know how tall the tree will be in 10 years, we would tell them
that the predicted height is 26 feet. (The numbers are simple enough
that you can check your code by doing the arithmetic in your head.)
y = mx + b
That is, it should report the input and the output, along with some nice descriptive text.
Will be posted later, visit again after
For the quiz questions:
1. D. All of them are okay.
2. A or B but not C
3. D. All of the above
4. C. Line breaks aren't allowed.
5. D. It displays "181"
6. B. The plus sign means concatenation (in this code).
Here's the solution to the JS Fiddle activity.
var height0 = 6;
var slope = 2;
var years = prompt("how many years?");
var height = slope*years + height0;
alert("in "+years+" years, it will be "+height+" feet high");