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JavaScript JavaScript Foundations Functions Review of JavaScript Functions

Posted by Nicholas Lee
Nicholas Lee
12,474 Points

Why is an error thrown, color is not defined?

In the following code, what will be output by the console.log call? 

function example ( ) {
  var color = "red";
  return color;
}

example("blue");

console.log(color);

Why is "blue" not passed though the parameters as a new argument?

2 Answers

Dino Paškvan
PLUS
Dino Paškvan
Courses Plus Student 44,108 Points
Dino Paškvan
Dino Paškvan
Courses Plus Student 44,108 Points

The color variable is defined for the scope of the example function. It does not exist outside of the function, so that's why the console.log results in a reference error.

The string "blue" is passed to the function as a parameter, but you're not doing anything with it inside the function. Also, your function doesn't have a named parameter so the only way to access it would be through the arguments Array-like object.

Jim Withington
Jim Withington
12,025 Points

This is from one of the JavaScript Foundations quizzes, just so you know. :-)

My follow-up: if we adjusted it like this, how come the console.log here doesn't display anything?

function example ( ) {
  var color = "red";
  return color;
  console.log(color);
}

example("blue");

Is there a way to get the console to display that color?

J Scott Erickson
J Scott Erickson
11,883 Points
J Scott Erickson
J Scott Erickson
11,883 Points

The global scope doesn't have access to the color variable that you have defined in the function. Unless you are missing some code where here is another 'color' variable defined anything outside of the scope of the function doesn't have any 'visibility' or 'knowledge' of the color variable.

This:

example("Blue");

Doesn't actually do anything, as the function definition does not have any arguments accepted and doesn't set the color variable based on a passed argument.

console.log(color);

will throw a reference error because, as I stated before, color is a variable only in the scope of the example() function and console has no visibility into it.