dataTypes.js

const index = 1;
((arg) => { arg++ })(index);
console.log(`Index: ${index}`);

const str = "a";
((arg) => { arg.toUpperCase() })(str)
console.log(`String: ${str}`);

const obj = { index: 1, str: "a" };
((arg) => { arg.index++; arg.str.toUpperCase(); })(obj);
console.log(`Object ${JSON.stringify(obj)}`);