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Welcome back.

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So in this lesson we're going to pick up right where we left off and we're going to see how do we change

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together simple or boolean statements like the one we just saw into more complicated statements that

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have multiple components.

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So they're still all going to evaluate to be true or false at the end of the day.

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But there might be multiple pieces that individually evaluate to be true or false before the entire

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thing becomes true or false.

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So there are three logical operators and like we said this is this is basically a way to chain together

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fully in logic.

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So those three are called AND OR and NOT.

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So we're going to start talking right.

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And and the way that works.

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First of all you write it with two ampersands and you can see right here we're using it in an example

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where x is equal to 5 and Y is equal to 9.

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So and takes two sides.

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There is a left side and a right side and goes in the middle.

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So the way you would read this is X less than 10 and X not equal to 5.

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So we'll evaluate both sides.

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X is less than 10.

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That is true.

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Five is less than 10 x is not equal to 5 and that is false.

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So we end up with true and false.

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And the way that works is that it requires both sides to be true.

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It requires both of them to be true Left and Right and that's not true in this case only the left side

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is true.

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So the entire thing is false.

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The way that or works is slightly different it still takes both sides.

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But it only requires that one of them be true left or right be true in order for the whole thing to

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be true.

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Just a side note the character here the pipe character is located above most peoples enter or return

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key and you usually need to hit shift to make it work.

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So two of those is how you write or in Javascript.

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So the Left Side Y is greater than nine.

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That is not true because Y has 9 or X is triple equal to 5 which is true X is 5.

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So we end up with false or true which evaluates to be true overall because or only requires one side

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to be true.

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Lastly we have not and the way that not works it's a little bit different.

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It doesn't take a left or right side it just negates or flips the value of what ever we apply it to

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.

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So if something was true and we put a knot in front of it it then becomes false.

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If something was false and we put a knot in front of it it then becomes true.

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So in this case the expression X triple equals Y which is false.

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Five is not equal to nine.

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So the inside is false but there is a bang or a knot in front of it which negates the whole thing and

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turns it to be true.

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So let's go ahead and give this a shot with a quick exercise.

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So below there are three lines of code.

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We have a variable x set to turn a variable y equal to the string A and then a short expression here

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that is using or in the middle.

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So go ahead and evaluate this yourself.

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Don't just copy and paste it into the console.

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We'll go over a solution.

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So just try and predict what the outcome is.

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If it is true or false based off of what we've covered so far.

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OK.

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So this exercise if we plug in 10 for X and the string A for y.

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Let's start on the left string a triple equals the string B.

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That is not true or x is greater than or equal to 10 which is true because X is 10.

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So we have false or true which gives us of course true.

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And we could definitely evaluate this over in the console just to verify our work just Center and you'll

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see that we get true.

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So one more exercise here.

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This time it's a little bit longer but it's the same basic components.

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So resist temptation just to type it into your cons..

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Make sure you plug in three for X and 8 for Y and see if you can figure out if the whole expression

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is true or false.

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OK.

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So hopefully you did that.

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Let's go over the answer now.

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So as I do this let's start by identifying the overall pattern here.

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So we've got a left side and a right side with an and in the middle.

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So we need both of these to be true.

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So let's start with the left side.

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We have X is 3 y is 8.

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So this first line X which is three the number double equals three the string that is true because double

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equals or.

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And this is a small point here.

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But technically if the left side of an OR statement is already true that means the entire statement

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is true.

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Javascript doesn't even care what's over here it's called short circuiting because we only need one

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out of two to be true.

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If we already get that on the left then we're done.

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But just to evaluate this for more practice X triple equals Y is false.

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Three is not the same as eight so this whole thing evaluates to true.

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However there's also a bang here.

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So that negates the whole thing to be false and just like before this actually short circuits the entire

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expression because we haven't and here and if the left side is false that means the entire and must

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be false because we were looking for two out of two and if we've already missed one and this is false

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then it doesn't matter what's over here.

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So the whole thing is false.

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But just to verify that.

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Let's go over to this side.

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So we have an and in the middle Why is not equal to 8.

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That is false and we haven't and in the middle.

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So that short circuits one more time.

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This entire thing.

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Because if we have the left side is already false then it doesn't matter what the right side is.

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But just to double check once again X is less than or equal to Y three is less than or equal to 8.

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That is true.

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So we end up with false and true which is false.

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And then we negate that whole thing.

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So that gives us true.

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So we have false and true.

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So that evaluates to be false.

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And just to double check you can paste it into the con..

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And if we do that we get false.

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So we have one less thing to cover here which is this idea that every value in javascript is inherently

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truthy or falsie.

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So aside from the obvious bully and true and false which are clearly true or false every other value

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has this inherent truthiness or falseness that javascript assigns them.

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So I'm going to open up my console and just show you a way of finding this out.

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So if I just want to know if the string hello is true or false see if I just type the string and hit

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enter it's just going to give me the string back.

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So what I can do is actually put it in a boolean statement and the simplest one is just to negate it

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.

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So if I negate the string hello and I get true back that tells me that the string hello is falsie because

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I indicated Likewise if I get false back that tells me that the string hello is truthy and I do get

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false which means that the string hello is Trixy.

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The other thing that I can do is double negated which will flip it and then flip it back and tell me

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that it's truthy.

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And likewise I can do the same thing on an empty string and you'll see that it's an empty string is

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actually falsie.

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Same thing with no

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0 not a number.

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And when you do negative 1 you'll see that it's actually true.

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So these are things that in some languages behave a little bit differently.

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So just because in javascript negative one is truthy that does not mean that in other languages it is

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automatically Trixy.

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So here's a quick recap.

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The hard rule is that the values false zero empty string no undefined and not a number are always falsie

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and everything else is truthy.

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So we have one less exercise here which is just like the others except now it's testing truthiness and

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faultiness.

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So three strings and empty string string ha ha and the string false.

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Evaluate this don't just run the consul we'll go over solution.

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Plug in the values mentally and see what you come up with.

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It's a whole thing true.

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Or is the whole thing false.

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OK.

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So the answer here is plug in string message and is funny.

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So you'll notice that we have an oar and something else.

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So let's go ahead and solve this first.

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Or on the left.

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So we have S T R or string which is an empty string which is falsie.

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So false or the string ha ha.

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Which is truthy.

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So false or true which gives us true for this little section here.

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Then we have true and is funny which is the string false which is which is a little tricky but the string

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falls could always double check is truthy.

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So that tells me that true and true is true.

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And the last thing you have to do is negate the entire thing which will give me false.

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So just to verify that you can copy this answer and I get false.

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Great.

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So in the next section we're actually going to see how we make decisions in javascript using these boolean

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logic expressions that we've just talked about.

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How do we run some code.

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If something is false how do we run some other code.

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If something is true