Create variables that can be accessed globally but can not be modified in the developer console

Question

How to create variables that can be accessed globally but can be modified only by a certain function?

Answer 1

Now with ecma 6 you can declare global variable with the keyword const, and these variables won't be modified.

const VARIABLE="wont be modified";

Moreover every time you create a function a closure is created. A closure is an inner function that has access to the outer function's variables, so you can create a function and work with it's closure

 (function(global){
        var a="I'm a";
        function modifyA(newvalue){
           a=newvalue;
        }
        function getA(){
           return a;
        } 
        global.modifyA=modifyA;
        global.getA=getA;      
    })(window);

console.log(typeof a,"a doesn't exist in global environment");
console.log(getA(),"but exist in getA's closure");
modifyA('I have a new value');
console.log(getA(),"A can only be modify it with modifyA function");

Answer 2

One way to accomplish something similar is to create a local function that would set the value and create a new 'get' function to return the value like:

function createObjectGetter(obj)
{
    this.getObject = function() { return obj; };
}

Then when you call it like createObjectGetter("abc"), from that point you can fetch the object like getObject() which will return "abc" while the value stays constant and is only adjustable through createObjectGetter() method.

Here's a reference: How can you make a variable/Object read only in Javascript?