JavaScript Review

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);

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

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;
}

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);

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

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

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

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!");
}

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);

Explain the difference between truthy and falsy values in JavaScript. Provide a few examples of both truthy and falsy values.

One of the falsy values in JavaScript is NaN. What is NaN? When might you encounter a variable that is storing NaN?

Explain the difference between the strict equality operator (===) and the equality operator (==).

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

Coding Problems

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