• I created a Singleton-like function for a Google Sheet of mine;
• Priv and Pub is my way of simulating Private and Public;
• When I assign its instance to a variable, I need to type ()() so it works the way I want it to. I want to be able to type Priv.whateverProp
• I've tried double parentheses in other places inside the Singleton function, but when I accomplish getting to use only one (), then the completions display apply, bind, call etc.
• Then I have to getInstance()().completions** again to access the instance properties, but when I run the program, it says SingletonFinder().getInstance() is not a function
• So I have to leave getInstance() with its single parentheses and type Priv().whaterverProp instead of Priv.whateverProp for the rest of the code, which I don't want.
• Why do I have to type it this way let Priv = SingletonFinder().getInstance()() ?

function GetFinder(){
    let Pub = {}
    let Priv = SingletonFinder().getInstance()()
    // the rest of the code...
}

function SingletonFinder() {
    let Priv = {}
    let Pub = {}

    /** @type {Class_Finder} */
    Priv.instance = null;
    Priv.createInstance = function () {
        return Class_Finder
    }
    Pub.getInstance = function () {
        if(!Priv.instance) {
            Priv.instance = Priv.createInstance()
        }
        return Priv.instance
    };
    return Pub
}

function Class_Finder() {
    // properties
}