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 as its assigned to the variable grade

Question 2

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

local variables function only within {}, global function across the entire code

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;
}

var stateTaxRate and var federalTaxRate are global, The var variables within calculateTaxes function are 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);

sum is not defined. addTwoNumbers needs to be assigned to a variable

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 function

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!");
}

If anything is entered except "Bob" nothing will happen

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.

Step over will execute the current line of code and pause on the next one. Step into will will enter the code of the current line and pause.

Coding Problems

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