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 is returning the value in the variable "grade"
Question 2

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

Local variable is one that exists within a function. Global variable is defined external from a function.
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 global variables. 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);
The alert that comes before the execution of the addTwoNumbers function does not have a value in the sum variable. There is no return statement. The sum variable is local to the function and will not be reached by the second alert 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(x)
Question 7

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

parseFloat(x)
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!");
}
You are assigning the string "Bob" to the firstName variable instead of checking for the expression to be true. Use ==
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);
20
Question 10

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

Stepping into will show the function / process for that line. Stepping over will move over the function call.

Coding Problems

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