Create a global counter in a NodeJS module

I am trying to create unique ids for my React components. I have created this modules:

var _uid: number = 0;

function getUid(): string {
    ++_uid;
    return `_uid_${_uid}`;
}

export default getUid;

Hoping that the _uid would be increased every time the module function is called, but it is always 1. How can I achieve increase it every time the module is required?

via Victor