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Hi there and welcome, this lesson is going to be about JavaScript immediately invoked function expressions

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so short for I, I f e and I'm going to be showing you in this lesson what they are and how they work.

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So I, Effy, are immediately invoked function expressions.

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So this is a JavaScript function that runs as soon as that is defined.

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And there are a lot of uses for these types of functions.

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It's a design pattern which is also known as self executing anonymous function, and it contains two

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major parts.

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There's some examples.

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Notice that it's also an anonymous function, so there's no name for it.

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And with the rounded brackets at the end of the function call, that allows it to immediately invoke

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the function.

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So there's also another example here where we're setting a variable when it comes to the scope of the

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variables so it can contain all of the variables within the scope of the function as it's being invoked.

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For example, where we've got first name equals Lowrance.

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It can't be seen outside of that function.

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There's also when we're declaring a function.

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So here we've got result.

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We can also immediately invoke that function, returning the first name.

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So in this case, the first thing that's going to be returned back is Lowrance.

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And you can also posehn Lawrence as a parameter into the function.

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When the function is being invoked.

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It's going to take that value of Lowrance as first name and it's going to output into the console the

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first name value.

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You can try this out within your editor.

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So there is a challenge for this lesson as well, and that's to output your name in the console using

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an immediately invoked function expression.

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And there's an example of the code that you can use in order to accomplish this.

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So go ahead and pause the video and I'll walk you through the solution to this challenge, as well as

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the other expressions that we just looked at.

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So what's the function itself?

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So they are anonymous functions.

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The structure works the same way where we've got a function and then we've got the block.

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A code is between the curly brackets.

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So the code block is in here.

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And then this is what we want to happen within this function.

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We can have the welcome output.

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And the way that we need to write the functions is we need to wrap it with the rounded brackets.

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And this alone, if you notice, that won't do anything yet because we're not invoking the function.

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So the last and final part of that function is to invoke it with the rounded brackets.

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So just as when you're creating a function and then you invoke the function with the round of brackets,

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it works the same way.

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And now you can see that that message gets output into the console so we can first name so passing in

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a variable and then adding in your name into the parameters.

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And then we can use the value that's been passed into the parameters and output that into the console.

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So when we refresh it, we get that variable being passed and notice as well.

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It works the same way again, as if we were to invoke the function and pass in an argument within this

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type of format.

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So it works the same way you can pass in multiple arguments.

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So all you have to do is comma, separate them and the structure is exactly the same as it was initially.

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So we also have the ability to create a function expression.

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I'm going to name it result.

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And using the immediately invoked function, we're going to return back a value here.

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And then this is what we're actually going to see being returned back as a value of result.

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So whatever, we're returning back and if we do Hello World and then we console logout the value of

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result, you're going to see that because this function is immediately invoking.

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And there was one thing that we did miss out here, and that's the rounded brackets to invoke the function.

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So we get Hello World.

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So this is the same thing as if we did result and we did the invoking of the function down here, we

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would get the same result.

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And if we missed the rounded brackets, we actually get the function code being returned back.

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So you can see that as well within the console.

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So if we're not invoking the function, it's not actually running through the code, it's just returning

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back all of the code that's associated with that function.

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And we do need those rounded brackets in order to invoke the function.

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Coming up next is going to be something new with Essex, where we're going to look at aero functions

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and this is going to be a short format for writing functions.

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So that's still to come.