JSFiddle - React, Tailwind, and code Playground

JavaScript

function createSomething(init, aaa) {
    function privateMethod(param) {
        return init[param];  //assuming this is more complicated, how can you test it?
    }

    function getData() {
        return init.data;
    }

    function getValue(name) {
        if (name === "privateNode" || typeof name !== "string") {
            return "permissionDenied";
        }
        return privateMethod(name);
    }
    // ----------------------------------
    if(aaa) return privateMethod;
    // ----------------------------------
    return {
        getData : getData,
        getValue: getValue
    };
}

var something = createSomething({
    privateNode : "allmysecrets",
    id : "1234",
    data : {
        stuff : "32t97gfhw3hg4"
    }
}, 1); // passing extra arg to get method

console.log(
    something('id'),
    something('privateNode')
) // 1234 allmysecrets