Pfthb

let's say I have a numeric variable (or any other type),
I want to convert this variable to a function which has the same variable name and returns the original value (without using additional variables)

var x=1
x=()=>x

this will copy x by reference, not by value, so the new x will always returns itself (i.e a function) not the original value

I reached the result using an additional variable (temp)

var x=1
var temp=x
var x=()=>temp

what I want is to copy this variable by value, not by reference
I know how to copy an object to another object, but it is not the same case

note: using the same name is important for the flow of the next code (i.e: I have to use a function, if another type provided, I have to convert it to a function of the same name)

Just write a function:

function constFunction(temp) 
 return () => temp;

so that you can call it as x = constFunction(x). Like every function call or assignment, this copies the value of the variable, not a reference. And no, you cannot really avoid a second variable (temp in this case), as you can't have x refer to both the function and the original value.