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All right, now I'll walk you through how
I would write the random number function.

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You learned how to create a random number
between two values in a previous course.

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The difference is that now you're using
a function that accepts arguments.

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For starters, I'll create
a function named getRandomNumber.

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I'm using a function decoration, but

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you could have written this as a function
expression or as an arrow function.

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The function should produce a random
number value between two numbers.

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So I need to add two
parameters to the function.

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I'll call them lower and upper.

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Next, I'll move the random number
code into the function and

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place the parameters
where they need to go.

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The upper value goes here, and
the lower value should go here and here.

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I'll assign the result to
a variable named randomNumber,

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Then return the value of randomNumber.

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You could make this
code even more compact.

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You don't need to assign
the formula to the variable,

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and then return the variable.

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Because the random number
generating code produces a value,

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you can return its result, like this.

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Let's look at why we can do this.

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This code accepts information,
the lower and upper values,

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and runs it through a couple of
JavaScript methods and does some math.

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All of this code evaluates, as programmers
say, to a single value, a random number.

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All a return statement
does is return a value.

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It doesn't matter where
that value comes from.

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It can be stored in a variable, or it can
be the result of another function, or

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a mathematical operation,
as it is in this case.

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All right, now to test this,
I'll call the function a few times and

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print the results to the console.

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First, I'll call getRandomNumber,
passing it the values 1 and 6.

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Below that,
I'll call getRandomNumber again,

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this time passing it 10 and 100.

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And I'll call getRandomNumber a third
time, passing it the values 200 and 500.

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I'll save my file, and
over in the console,

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I get three random numbers, good.

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So now I can use my random number
function in all sorts of ways.

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For example,
display it in a message, like this.

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Remember in a template literal,

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you can include any JavaScript expression
between the dollar sign and curly braces.

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And its value will be
inserted into the string.

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By expression I mean any code
that evaluates to a single value,

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like a variable, math operation, or
in this case, a call to a function.

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In the console, we see the message,
41 is a random number between 10 and 100.

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You might've added a default
parameter to your function too.

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For example, set the upper parameter
to a default value of 100.

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The getRandomNumber function
is working as expected.

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However, there's at least one situation
in which the function won't work.

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The two arguments passed to
the function must be numeric values.

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If you, for example,
call the function with a string like six,

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instead of the number 6,
the function will not work.

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Notice the value NaN.

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Part of being a good programmer is looking
for ways that your programs might break

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and then coming up with a plan
to handle those problems.

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To fix this, we can use an if statement
to make sure that both arguments

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are numbers and then display an error if
one or both of the values are not numbers.

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In the next video,
we'll implement the solution.