Is there a discrepancy in function scope between Chrome and Firefox? Which browser has the correct behavior?

When I run this JavaScript code in Chrome versus Firefox, I am noticing some differences in behavior:

var outer = function (param) {
  var inner = function (theinput) {
    return theinput * 2;
  };
  return 'The result is ' + inner(param);
};

console.log(outer(2));

console.log(inner(5));

Result on Firefox:
"The result is 4"
10

Result on Chrome:
"The result is 4"
undefined

It seems that because `inner` is declared with "var", it acts as a private function in Chrome. This is why the output shows as undefined when trying to access `inner` outside of its scope in Chrome. However, in Firefox, it appears to be treated differently, displaying the value of `inner` even when accessed externally.

If I were to remove the `var` declaration for `inner`, my understanding is that it would promote `inner` to a global function after its first execution. This would mean that my initial assumption about Chrome's behavior being correct due to the `var` keyword may not be entirely accurate.

Answer №1

It seems that the output in Chrome is correct because the function "inner" is declared as private due to being scoped with "var". It appears that Firefox has made an incorrect implementation.

Actually, neither browser's output is correct. The "inner" function is only accessible within the function assigned to "outer", so trying to access it outside of this scope will result in a ReferenceError when you call console.log(inner(5));.

This is the behavior I observed while testing your code on both Chrome and Firefox.

If the "var" keyword was removed from the declaration of inner, does it become a global function after its first execution? Am I understanding this correctly?

Yes, your understanding is correct (unless the code is running in strict mode, in which case attempting to assign a value to "inner" without declaring it with var inner would result in an error).

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