Understanding the Scope in JavaScript Functions

The function in the presented code snippet is fundamentally a demonstration of a JavaScript concept: scope. The correct answer is that the function returns the value in scape.

In JavaScript, variables can be defined in the global scope or within the local scope of functions. The 'scope' of a variable determines its accessibility throughout your code.

Here's how it works:

var scope = "global scope"; //global variable

function checkscope() {
  var scope = "local scope"; //local variable
  function func() {
    return scope; //accesses the closest scope variable
  }
  return func;
}

In the above code snippet, there are two variables named scope. One is in the global scope outside of any function, and the other is in the local scope, declared within the checkscope function.

Now, the important part is understanding what happens when checkscope is invoked and subsequently what happens when func is invoked.

When we call checkscope, it creates a new scope for its local variables. In this new scope, we're defining scope to be "local scope". The inner func function, when invoked, looks for the closest scope variable in its parent function which is the checkscope function and returns "local scope".

In JavaScript, an inner function always has access to the variables and parameters of its outer function, even after the outer function has completed its execution. This is a key concept in JavaScript known as a closure.

Thus, each function in JavaScript creates a new scope for variables and it's important to understand this concept when writing and testing your code. Beware of var reassignments that can happen accidentally when variable names are reused in different scopes.

Following this best practice of understanding scope can not only prevent bugs but it can also make the code more readable and manageable. You can always leverage tools such as linters to help identify such potential issues in your code.