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Welcome back in the previous video we discussed the third rule for determining the value of the key

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word this explicit binding.

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We learned that using call apply and bind can change the context of the key word.

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This Let's see how we can fix our previous issue by using call the first code block is identical to

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what we saw before.

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But let's see what's happening in the second section.

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Previously we were calling person dog dog say hello which was returning Hello.

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Undefined does happen because the value of the keyword this inside of the say hello function refers

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to the dog object which does not have a first name property.

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Since we're using call we can now change what we want the value of the keyword this to be.

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So let's change it to be the person object.

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Now that we've done that we can see that the function returns Hello called and our issue is fixed.

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We can also use the determine context function inside the dog object and change the value of the keyword

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this to make the function return true.

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One important thing to note is that we are not invoking the say hello or determine context method we

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just attach call onto it.

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So there are no parentheses after say hello and determine context.

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When we use call very commonly call is used to avoid code application like this example below.

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Here we have two objects cold and L.E. which both have a first name property and they say Hi method

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.

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While this code works totally fine we're repeating ourselves quite a bit inside of the elete object

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to say hi method inside of the object is identical to the same method inside of the cold object.

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How can we refactor our code and get rid of the high method inside of the object.

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What we really like to do is use the same high method from the cult object.

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But instead of the keyword this referring to cold we want to explicitly set it to be the L-E object

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.

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Pause the video now and see if you can figure out how to solve the problem using call.

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Let's take a look at a solution.

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We remove the say hi method from the object and we are using call to set the value of the keyword this

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to be L-E.

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When the say hi method is being invoked the first parameter to the call method is what we want the keyword

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this to refer to.

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We call that this ARG.

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Once again this stuff is quite tricky.

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So if you're feeling a bit confused look at the previous slide and make sure you type these examples

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into the chrome console to see exactly what's going on in the next video.

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We're going to take a look at apply and see how we can set the context of the keyword this using apply

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as well as passing arguments to the function in which we call apply.

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On the other