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In this video, we're going to take a look at another example of when we're going to add in a type annotation

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manually.

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So this is going to be whenever we declare a variable on one line and then initialize it later as a

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quick reminder type inference only works when we do a variable declaration and initialization on the

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same line.

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And so, obviously, if we split this into two separate steps or two different lines of code, then

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type inference doesn't work anymore.

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All right, so I'm going to put back over to my editor again at the very bottom of my variables file.

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I'm going to set up a second example here.

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I'm going to say when we declare a variable on one line and initialize it later.

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OK, so for this example, I'm going to make an array of strings called words like so and I'm going

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to give this the words red.

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Green and blue.

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Then right after that, I'm going to declare a variable called bound word like so.

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So here's what I want to do, I want to write a for loop that's going to iterate through this array

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right here.

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And if I ever find a word or a string equal to green, then I want to set found word to true.

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So if you find green inside of words just set downward to true, that's pretty much it.

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I know this is a silly example, but I just want to give you a very practical example of when we're

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going to run into this type annotation stuff that's going to write out my for loop.

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I'm going to say let equals zero I less than words length I plus plus.

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And then for every word will say, if words at eye is equal to green and we'll set found word equal

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to true like so.

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It's now in this case, I have an instance where I'm declaring the variable up here and then I only

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assign it a value or initialize it down here inside of my for for a loop.

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If I know mouseover found word and will very clearly tell me that this is of type any and in fact I

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even have a little underline here, that is a warning that tells me that found word has an implicit

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any type.

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And then the tip here says that I might get a better type if I actually use the variable.

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Now, when it says inferred from usage, that actually means that, like I have to add in the annotation

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right here or optionally initialize it on the same line.

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So in this case, to make this morning go away, we have to add in a type annotation so I can tell,

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TypeScript.

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All right, there's going to be a boolean.

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And now we get around that issue, so it never type inference doesn't work because we are doing declaration

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and initialization on separate lines.

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We're going to add any type annotation.

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That's pretty much it.

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Now, as a quick aside here, obviously the best way to write out this code would have been to do something

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like this, to initialize found where it is false.

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And now TypeScript understands what's going on here.

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This is way better code than what we had before.

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But again, I just wanted to give you a quick example of where we might have a declaration on one line

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and then initialization at some future point.

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All right, so let's take a quick pause right here.

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When we come back in the next video, we're going to take a look at our final example of when we are

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going to prefer to use a type invitation.

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It's a quick pause and I'll see you in just a minute.