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);
CalculateLetterGrade returns a value, because the result is the grade variable.
Question 2

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

The local bariable is declared inside a function and is only accessible inside the function, while the Global variable is declared outside any function, and is accessible throughout the script
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;
}
stateTaxRate and federalTaxRate are both global, while totalStateTaxes, totalFederalTaxes, and totalTaxes are local variables
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);
Sum is declared as a local variant inside the addTwoNumbers function
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')?

parseFloat
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 uses the assignment operator instead of the equality operator
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);
x will equal 18
Question 10

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

Stepping over executes the current line of code and moves to the next line, while stepping into moves into the called function if the current line contains a function, and it continues debugging line by line in the function

Coding Problems

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