Passing arguments to functions

message is being used as a placeholder. The goal for building functions is to have the intent to RE-USE them.

When you pass-in an argument you are kind of declaring a variable, it's kind of like saying "this is, whatever I say it is, whenever I say it is"

Your other example wouldn't work because you have no string attached to the var message.

function print(thisWillBeTheContentToPutIn) { 
    var div = document.getElementById('output'); 
    div.innerHTML = thisWillBeTheContentToPutIn; 
}

In your example... for it to work:

function print() { 
var message = thisIsTheContent;
div.innerHTML = message; 
var div = document.getElementById('output'); 
}

In the first example, the message can be ANYTHING. print('cheetos');

The second can only be what you declared locally to that function. print();

When you pass-in an argument you are kind of declaring a variable, it's kind of like saying "this is, whatever I say it is, whenever I say it is"

Understood. So it's a placeholder until you decide what to do with it.

And after that it holds the content or value of whatever you assigned it to?

Also, could you pass in the placeholder, AND a previously declared variable?

function print(message, previouslyDeclaredVariable) {

};

I don't see any reason to, but that doesn't mean I really know beyond a shadow of a doubt that you can't.

I'm pretty sure (90%) you can't though, because those arguments are local and specific to that function alone.

You won't use the arguments outside of that function, i.e,

red = 'hello';
green= 'darkness';
blue = 'myoldfriend';

function color(red, green, blue) {
   red= red;
   green=green;
   blue= blue;
   console.log(red + green + blue);
}

console.log(red + ' ' + green + ' ' + blue);
color('way','down', 'yonder');

both results in two different things.

Instead of declaring in the function that red is now 'way', I gave it an argument that says hold this until I tell you what to do with it. In this instance I call it 'way'... if I wanted to, it could be 'caddywampus', etc. That's the power of local variables, and arguments.

When I console.log the variables, those are global, so the console.log doesn't recognize, or even see the variable change in the function.

I wouldn't think of using an argument to declare my variables within the argument parameters, rather I would say I have an argument, and inside the function assign the argument to the variable.

Here's something too, if you use arguments in your function, YOU HAVE to use them within your function.

this:

function balls(x) {
    console.log('I have none');
}
 is a no-go.

function balls(x) {
  console.log('I ' + x + ' something');
}

balls('ate');

// the console will log "I ate something"