JavaScript Variables and Data Types Worksheet
Question 1Find a reference that lists all the keywords in the JavaScript programming language.
Question 2True or false: keywords and variable names are NOT case sensitive.
There are some rules for how you can name variables in JavaScript. What are they?
- Must begin with a letter, underscore (_) or dollar sign ($)
- Cannot start with a number
- Can contain letters, numbers, underscores, and dollar signs
- Cannot be a reserved keyword (e.g.,
var,function) - Case sensitive (
myVarandmyvarare different)
What is 'camelCase'?
What are ALL the different data types in JavaScript (note that there are some that we did not discuss in class)?
StringNumberBooleanUndefinedNullSymbol(ES6)BigIntObject(including Arrays, Functions, etc.)
What is a boolean data type?
true or false.
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;
var lastName = Jones;, JavaScript will throw an error because "Jones" is not defined.
What character is used to end a statement in JavaScript?
; is used to end a statement in JavaScript.
If you declare a variable, but do not initialize it, what value will the variable store?
undefined.
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);sumis the result of98 + "88"- Because one value is a string, JavaScript performs string concatenation
- Output:
9888string(data type ofsum)
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);console.log("total");prints the stringtotalconsole.log(total);prints the value of the variabletotal, which is99
What is the difference between these two variables?
const score1 = 75;
const score2 = "75";score1is a numberscore2is a string that looks like a number- This matters when doing calculations, as string and number behave differently
Explain why the this code will cause the program to crash:
const score = 0;
score = prompt("Enter a score");score is declared with const, which means its value cannot be changed.
But the next line tries to reassign a new value using prompt(), causing an error.
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!