JavaScript Review

Question 1

There are two functions being called in the code sample below. Which one returns a value? How can you tell? 

var grade = calculateLetterGrade(96);
submitFinalGrade(grade);
The variable "grade" iis being returned because calculateLetterGrade and submitFinalGrade are being stored in the variable.
Question 2

Explain the difference between a local variable and a global variable.

Local Variable is a variable being declared within a block of code and Global Variable is beinig declared and accessed from anywhere within the program.
Question 3

Which variables in the code sample below are local, and which ones are global? 

var stateTaxRate = 0.06;
var federalTaxRate = 0.11;

function calculateTaxes(wages){
	var totalStateTaxes = wages * stateTaxRate;
	var totalFederalTaxes = wages * federalTaxRate;
	var totalTaxes = totalStateTaxes + totalFederalTaxes;
	return totalTaxes;
}
federalTaxRate and stateTaxRate are global and everything else is local.
Question 4

What is the problem with this code (hint: this program will crash, explain why): 

function addTwoNumbers(num1, num2){
	var sum = num1 + num2;
	alert(sum);
}

alert("The sum is " + sum);
addTwoNumbers(3,7);
You didn't need to alert it two times, you can just get rid of the second alert code.
Question 5

True or false - All user input defaults to being a string, even if the user enters a number.

True.
Question 6

What function would you use to convert a string to an integer number?

ParseInt.
Question 7

What function would you use to convert a string to a number that has a decimal in it (a 'float')?

Float function.
Question 8

What is the problem with this code sample: 

var firstName = prompt("Enter your first name");
if(firstName = "Bob"){
	alert("Hello Bob! That's a common first name!");
}
It didn't have a code that if someone were to put a different name it would be a different alert than the same when you put in Bob.
Question 9

What will the value of x be after the following code executes (in other words, what will appear in the log when the last line executes)? 

var x = 7;
x--;
x += 3;
x++;
x *= 2;
console.log(x);
A number would appear when the log is executed which is 20.
Question 10

Explain the difference between stepping over and stepping into a line of code when using the debugger.

Stepping into the code observes the code and runs inside the body of the function. Stepping over will quickly execute all of the lines of the code in the function and the debugger will move to the next line.

Coding Problems

Coding Problems - See the 'script' tag at the bottom of the page. You will have to write some JavaScript code in it.