JavaScript Variables and Data Types Worksheet

Question 1

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

Modzilla

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?

Must start with a letter, cannot start with a number. cannot used reserved keywords like var, let , if or function.

Question 4

What is 'camelCase'?

A naming convention where the first word is written in all lowercase, and every word folling starts witha captial letter.

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, BigInt, Boolean, Undefined, Null, Symbol, Object

Question 6

What is a boolean data type?

Logical data type that can only have two values: 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;

JavaScript treats the word as a varible name rather than a literal piece of text

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);

The + operator between a number and a string does not mathematically add the numbers. It would show 9888

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);

It would output total and 99

Question 12

What is the difference between these two variables?


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

score1 is a number and can be used for mathematical equations score2 is a string text which just puts the two numbers together but does not add them together.

Question 13

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


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

The keyword const means the variable is a constant, so its value cannot be changed after it is assigned.

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!