Dynamic variable in Javascript (call by reference)

Question

When a variable refers to an object the value is a reference to the object (Referred from: Javascript by reference vs. by value )

function fun1(obj) {
obj.first = 1; //it affects the object ->obj
}
var myObj1 = {first: 0};
fun1(myObj1); //sending the object to the function
console.log(myObj1.first); // 1

But I would like to change the variable from an object, for example

function fun2(obj) {
obj = 1;      }
var myObj2 = {first: 0};
fun2(myObj2.first);
console.log(myObj2.first);

Is there any way to achieve this?

Answer 1

Is there any way to achieve this?

Not directly. All you can do is pass an object and have the function modify a property on it, as in your first example. JavaScript does not have pass-by-reference, just pass-by-value. (The value may be an object reference, of course, but it's still a value.) There's no way in JavaScript to directly modify the variable/property you're passing into the function, because what the function receives is a copy of the value of that variable/property, not a reference to that variable/property.

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Just to be clear about something: In your first code block, you said you were "sending the object to the function." That's incorrect. You send a reference to the object to the function.

This is the key thing to understand: Variables, properties, and function arguments (collectively, "variables") contain values, and those values are copied when you use assignment or when you pass them into functions. The value that refers to an object is called an object reference, because the value isn't the object, it's a reference to (pointer to) the object elsewhere in memory. The reference is copied when you pass it into a function, the object is not.

Don't confuse the "reference" in "object reference" with the "reference" in "pass-by-reference," they're completely different things. (In pass-by-reference, the reference is to the variable, not an object. JavaScript doesn't have pass-by-reference.)