在另一个函数内的settimeout中更改变量

Question

I'm trying to create reusable function that has settimeout function inside that will change the variable passed to the first function.

let variable = true;


reusablefunction = (passedvariable) => {


    setTimeout(() => {

        passedvariable = false;
       // this turns out true for some reason

    }, 1, passedvariable);
  };



// Change value of passed variable (variable) to false after a timeout 

reusablefunction(variable);

Answer 1

You can't. When you do

reusableFunction(variable);

the value of variable is passed into the function, not the variable itself. The parameter passedVariable is not in any way connected to variable . That is, you end up with something like this in memory:

+−−−−−−−−−−−−−−−−−+
| variable: false |
+−−−−−−−−−−−−−−−−−+

+−−−−−−−−−−−−−−−−−−−−−−−+
| passedVariable: false |
+−−−−−−−−−−−−−−−−−−−−−−−+

You could pass in an object and have the function update a property on it instead:

let obj = {
    prop: true
};

let reusablefunction = (passedObject) => {
    setTimeout(() => {
        passedObject.prop = false;
    }, 1); // No need to pass the parameter here
};

reusablefunction(obj);

With that, you end up with something like this in memory:

+−−−−−−−−−−−−−−−+              
| obj: Ref55461 |−−−−−−−−−−−−−+
+−−−−−−−−−−−−−−−+             |
                              |          +−−−−−−−−−−−−−+
                              +−−−−−−−−−>|   Object    |
                              |          +−−−−−−−−−−−−−+
+−−−−−−−−−−−−−−−−−−−−−−−−+    |          | prop: false |
| passedObject: Ref55461 |−−−−+          +−−−−−−−−−−−−−+
+−−−−−−−−−−−−−−−−−−−−−−−−+

Since both obj and passedObject refer to the same object, you can change its properties via either of them.

---

That said, there may well be a better way to solve the underlying problem you're trying to solve...