JSFiddle - React, Tailwind, and code Playground

JavaScript

//By Pavlo M. Public domain

    "use strict"
    
    //return text that will reference variable by name (by capturing that variable to closure)
    function byRef(varName){
    	return "({get value(){return "+varName+";}, set value(v){"+varName+"=v;}})";
    }
    
    //demo
    
    //assign argument by reference
    function modifyArgument(argRef, multiplier){
    	argRef.value = argRef.value * multiplier;
    }
    
    (function(){
    
    var x = 10;
    
    alert("x before: " + x);
    modifyArgument(eval(byRef("x")), 42);
    alert("x after: " + x);
    
    })()