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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Passing an Argument to a Function

Dayne Wright
Dayne Wright
11,235 Points
Posted by Dayne Wright
Dayne Wright
11,235 Points

Why do you not need to create a parameter in a function with var?

I am curious as to why you do not need to create a variable first for the parameter you pass into a function. Is there a reason why it does not need it?

1 Answer

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,253 Points
Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points

I think it's because this challenge is asking you to create a variable in local scope. And that's what you're doing when you're passing in the parameter to the function returnValue. At the parameter stage, your first argument is a placeholder variable which is then given a value at function call. 

function returnValue(one) {

   return one;
}

var echo = returnValue("My argument");

It's only when the function is called in the last line that JS knows what value to display in the "one" placeholder variable. :-)