Pass a global variable to a function for reassignment in javascript

Question

I am trying to create a helper function that in part takes in a global variable for reassignment. Trying to avoid using eval to make this work.

let oneQuestionCount,
    twoQuestionCount,
    oneQuestionsChecked,
    twoQuestionsChecked;

function hideFadeIn(divToHide, divToShow, countItem = null, checkedItem = null) {
    $("div#item-" + divToHide).hide();
    $("div#item-" + divToShow).fadeIn();
    if (countItem) {
      countItem = $("div#item-" + divToShow + " :input").length; // want the global var to be changed not the function scope var
    }
    if (checkedItem) {
      checkedItem = $("div#item-" + divToHide + " :checked").length; // want the global var to be changed not the function scope var
    }

hideFadeIn(
      "one",
      "two",
      twoQuestionCount, // how to pass in and change globally?
      oneQuestionsChecked // how to pass in and change globally?
    );

console.log(twoQuestionCount, oneQuestionsChecked); // should be reassinged value by the function.

There will be multiple function calls and other global variables that need to be assigned - hence the helper function. ex: hideFadeIn("one","two",twoQuestionCount, oneQuestionsChecked); then hideFadeIn("two","three",threeQuestionCount, twoQuestionsChecked); then hideFadeIn("three","four",threeQuestionCount, fourQuestionsChecked); etc...

Answer 1

You can't do that. When you pass twoQuestionCount into hideFadeIn , its value is passed, not the variable.

If you like, you could put those in an object, and then pass in the object:

let whatever = {
    oneQuestionCount: 0,
    twoQuestionCount: 0,
    oneQuestionsChecked: 0,
    twoQuestionsChecked: 0
};

then

hideFadeIn("one", "two", whatever);

hideFadeIn can change the properties on the object it receives.