JavaScript Variables and Data Types Worksheet

Question 1

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

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?

Variable names must start with a letter, an underscore (_) or a dollar sign ($). Variable names cannot contain spaces. Variables cannot be the same as reserved keywords such as if or const. By convention, JavaScript variable names are written in camelCase.
Question 4

What is 'camelCase'?

The first word is lowercase and each word after is started with an uppercase 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 A text of characters enclosed in quotes Number A number representing a mathematical value Bigint A number representing a large integer Boolean A data type representing true or false Object A collection of key-value pairs of data Undefined A primitive variable with no assigned value Null A primitive value representing object absence Symbol A unique and primitive identifier
Question 6

What is a boolean data type?

A data type representing 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;

If quotes are forgotten around a string when initializing a variable in JavaScript, the interpreter will attempt to interpret the unquoted text as a variable name, property name, or a reserved keyword.
Question 8

What character is used to end a statement in JavaScript?

A semicolon;
Question 9

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

If a variable is declared but not assigned a value, it will hold the special value 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 output will be "9888" and "string" because the number is coerced into a string during concatenation.
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);
prints the literal string "total" console.log("total"); // prints the variable value console.log(total); // preferred: print a label and the value console.log("total:", total); console.log(`total = ${total}`);
Question 12

What is the difference between these two variables? 


const score1 = 75;
const score2 = "75";
score1 is a number data type, while score2 is a string data type.
Question 13

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


const score = 0;
score = prompt("Enter a score");
The code will cause a crash due to an attempt to reassign a constant variable.

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: