JavaScript Variables and Data Types Worksheet

Question 1

Find a reference that lists all the keywords in the JavaScript programming language.

JS Keywords

Question 2

True or false: keywords and variable names are NOT case sensitive.

False

Question 3

There are some rules for how you can name variables in JavaScript. What are they?

Names can contain letters, digits, underscores(_) and dollar signs($)
Names must begin with a letter
Names can also begin with $ and _
Names are case sensitive
Keywords cannot be used as names

These rules were obtained from here under the JavaScript Identifiers section.

Question 4

What is 'camelCase'?

Start the variable in lowercase and when you get to the next word use an uppercase letter as the first character and then go back to lower case. ex: thisIsAnExampleVariableName

Question 5

What are ALL the different data types in JavaScript (note that there are some that we did not discuss in class)?

String
Number
Boolean
Bigint
Undefined
Null
Symbol
Object

This list was obtained here.

Question 6

What is a boolean data type?

True or False

Question 7

What happens if you forget to put quotes around a string when you initialize a variable to a string value? How does JavaScript try to interpret this?
For example: var lastName = Jones;

In the example, it would treat Jones as another variable and not a string.

Question 8

What character is used to end a statement in JavaScript?

; (semicolon)

Question 9

If you declare a variable, but do not initialize it, what value will the variable store?

undefined

Question 10

What output will the following program produce? In other words, explain what you would see in the console log if you ran a program like this:


const firstTestScore = 98;
const secondTestScore = "88";
const sum = firstTestScore + secondTestScore;
console.log(sum);
console.log(typeof sum);

string because the variable secondTestScore has "" around its initializing which treats it as a string

Question 11

What output will the following program produce? In other words, explain what you would see in the console log if you ran a program like this:


const total = 99;
console.log("total");
console.log(total);

total
99

the word total would be on 1 line in the console and the next would be 99

Question 12

What is the difference between these two variables?


const score1 = 75;
const score2 = "75";

score1 is a number datatype
score2 is a string datatype. It will be treated as text instead of the number.

Question 13

Explain why the this code will cause the program to crash:


const score = 0;
score = prompt("Enter a score");

score is declared as a constant variable meaning it cannot changed and the second part of the code is trying to changed the constant variable. You would have to use let instead of const.

Coding Problems

Coding Problems - See the 'script' element below this h1 element. You will have to write some JavaScript code in it.

Here are some tips to help you with the coding problems:

To do this assignment, you'll need to know how to open the brower's developer tools (press F12) and look at the console log.
Pay extremely close attention to syntax! One little syntax error can mess up your entire program.
After you complete each problem, refresh the page in the browser and look in the console your log message and for errors.
If you have an error in the console, check the line number of the error then look for syntax errors on that line (and the line before and the line after that line).
If you get stuck on this assignment, please ask for help! Dealing with syntax errors can be extremely frustrating for beginners. It takes a lot of effort and support to get comfortable with the syntax of a language. Don't be afraid to ask for help, your success in this class will depend on your willingness to get help!