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JavaScript JavaScript Basics (Retired) Creating Reusable Code with Functions Giving Information to Functions

Konrad Dziekonski
Konrad Dziekonski
7,798 Points
Posted by Konrad Dziekonski
Konrad Dziekonski
7,798 Points

little modification

Hello,

I have tried to modify Daves code a little by defining third parameter in the getArea function:

function getArea(width, length, unit) { var area = width*length; var unit = 'm2'; return area + "" + unit; }

console.log(getArea(10, 20, unit));

but the console is returning: Uncaught reference error: unit is not defined at random.js:7

could you please explain why is it not working? I thought that if I would store a value of string 'm2' in a variable called unit I could use it than in a way like the function knows that it has to multiply width by length. But hmm why is it stored in variable "area" but the keyword "area" has not been used, what for was it stored in this variable?

I have also tried to delete the third parameter from the function:

function getArea(width, length) { var area = width*length; var unit = 'm2'; return area + "" + unit; }

console.log(getArea(10, 20, 'm2'));

but left it in the console log and it appeared in the console log screen, so why was it necessary to declare the third parameter - unit?

if that make sense at all... i mean my qustion ;] thanks

Henry Bown
Henry Bown
30,839 Points

If you're passing unit as one of the parameters, you don't need to set it as a variable separately. 

function getArea(width, length, unit) { 
  var area = width * length; 
  return area + " " + unit; // Added a space between the quotes to separate area and units, if you're not including a space there is no reason to concatenate the string.
}

console.log( getArea( 10, 20, 'm2' ) );

This snippet will output "200 m2" to the console. 

function getArea(width, length) { 
  var area = width * length; 
  var unit = 'm2';
  return area + " " + unit;
}

console.log( getArea( 10, 20 ) );

This will also output '200 m2'

The reason you're getting this error is due to defining the variable inside the function. The code that effectively is running is similar to:

  console.log(favFood);
  var favFood = "ice cream";

So at the time that it is calling the variable, it isn't defined.