How to Create v4 Bitly Short link using JavaScript?

Question

We want to migrate v3 to v4 bitly using javascript. We were using below code in v3 bitly:

var x = "";
$.bitlr({
    apiKey: '......',
    link: longurl,
    anchor: false,
    success: function (newLink) {
        x = newLink;
    }
});
return x;