# JS Tip of the Day: Parameters are Reference Variables

**URL:** <https://forum.kirupa.com/t/js-tip-of-the-day-parameters-are-reference-variables/643093>\
**Category:** web dev\
**Created:** [May 13, 2020, 2:09pm UTC](https://forum.kirupa.com/t/js-tip-of-the-day-parameters-are-reference-variables/643093 "2020-05-13T14:09:12Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![senocular](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/senocular/32/7217_2.png) [@senocular](https://forum.kirupa.com/u/senocular)\
**Post date:** [May 13, 2020, 2:09pm UTC](https://forum.kirupa.com/t/js-tip-of-the-day-parameters-are-reference-variables/643093/1 "2020-05-13T14:09:12Z")

</div>

**Parameters are Reference Variables**  
Level: Advanced

JavaScript doesn’t support reference variables - variables that, when assigned, also apply their assignment to the variable that they reference (not to be confused with JavaScript object references). In C++, for example, you can specify a reference variable using `&`.

```cpp
// C++
int main() {
   int x = 1;
   int& y = x;

   y = 2;
   std::cout << x; // 2
}

```

There is, however, a weird quirk in JavaScript where you _can_ see reference variable-like behavior at work. This happens with function parameters and the `arguments` object. In the right circumstances, if you redefine a function parameter, the `arguments` object will also reflect that changed value and vice versa.

```javascript
// JavaScript
function showRefs (a, b) {
    console.log(arguments); // [1, 2]
    a = 3;
    b = 4;
    console.log(arguments); // [3, 4]
    arguments[0] = 5;
    arguments[1] = 6;
    console.log(a, b); // 5, 6
}
showRefs(1, 2);

```

This is not a behavior you should depend on. In fact, it does not occur in strict mode or when there’s anything fancy happening in the parameter list such as default parameters or a `...rest` parameter. But, if you are using the `arguments` object, it’s something to be conscious of, especially if you’re modifying parameter variables or mutating `arguments` (which you probably shouldn’t be doing anyway).

More info:

- [arguments on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments)