Answer the following questions:

• What does the throw keyword do? The throw keyword allows you to return an error/exception of your choice
• What is the difference between a TypeError and ReferenceError TypeErrors occur when JavaScript is unable to perform a certain operation on a data type (invoking something that is not a function, accessing properties on something that is not an object). ReferenceErrors occur when JavaScript does not have a reference to the variable in memory (accessing a variable that is not defined or not in the current or outer scope)
• How do you create a snippet in the chrome dev tools? Open the sources tab, head to the left hand panel and click on snippets, then right click inside the tab and click 'new'
• In the chrome dev tools, inside the sources tab, there is a "pause" button which allows you to "pause on caught exceptions". What is an exception? An exception is an error that occurs in your program. Caught exceptions are errors that are evaluated in a try/catch block
• How do we "catch" errors in JavaScript? Give an example with code for what that might look like We catch errors using a try/catch block

try {
   undefined()
} catch(e){
	console.log("We just made a TypeError, we can learn more using the error object returned to us:", e);
}

Explain what type of error will be thrown, why the error is occuring and how to fix it:

person;

Type of error - ReferenceError

Why - Because we are accessing a variable that has not been defined

var data = {};
data.displayInfo();

Type of error - TypeError Why - The value of data.displayInfo is undefined, so we are invoking undefined which we can not do. Undefined is not a function

var data = {};
data.displayInfo.foo = "bar";

Type of error - TypeError Why - **We are trying to assign a property of foo on undefined. Undefined is not an object so we can not do that. **

function data(){
    var thing = "foo";
}
data()
thing;

Type of error - ReferenceError Why - The thing variable is only available in the scope of the data function. We are trying to access it out of scope and JavaScript does not have a reference to it

Fix the broken code and explain what was wrong:

for(var i=0; i > 5; i++){
    console.log(i)
}

FIX

for(var i=0; i < 5; i++){
    console.log(i)
}

What was wrong - our condition inside the loop was not correct

function addIfEven(num){
    if(num % 2 = 0){
        return num + 5
    }
    return num;
}

FIX

function addIfEven(num){
    if(num % 2 === 0){
        return num + 5
    }
    return num;
}

What was wrong - we were using assignment with = in our if statement, not comparison with == or ===.

function loopToFive(){
    for(var i=0, i < 5, i++){
        console.log(i)
    }
}

FIX

function loopToFive(){
    for(var i=0; i < 5; i++){
        console.log(i)
    }
}

What was wrong - our syntax was incorrect inside the loop. We separate each section of a for loop with a ; and not a ,

function displayEvenNumbers(){
    var numbers = [1,2,3,4,5,6,7,8]
    var evenNumbers = []
    for(var i=0; i<numbers.length-1; i++;){
        if(numbers % 2 = 0); {
            evenNumbers.push(i)
        }
        return evenNumbers;
    }
}
displayEvenNumbers() // should return [2,4,6,8] 

// HINT - eight things need to be changed here for this to work! Start by fixing the syntax errors and then run the function to see what your output is

FIX

function displayEvenNumbers(){
    var numbers = [1,2,3,4,5,6,7,8]
    var evenNumbers = []
    for(var i=0; i<numbers.length; i++){
        if(numbers[i] % 2 === 0) {
            evenNumbers.push(numbers[i])
        }
    }
	return evenNumbers;
}

What was wrong - The following errors

1. Each part of the for loop should be separated by a ; not a `,'
2. The for loop should not have a final ;
3. The if statement should not have a ; after the condition
4. We should loop until i < numbers.length or i <= numbers.length-1and not numbers.length-1
5. We can't use assignment (=) inside of the condition, we have to use comparisson (== or ===).
6. We need to make sure our if condition checks the value we are at in the numbers array (numbers[i]) and not the entire numbers array
7. We need to push into our evenNumbers array, the value not the index numbers[i] instead of i.
8. We need to make sure we return after the loop has finished and not after the if statement.