Here is my code and it works as expected.

function Afunction(v) {
    this.v = v;
}
Afunction.prototype.vlog = function () { console.log(this.v); };

function extend(props) {
    for (const key in props) {
        const prop = props[key];
        Afunction.prototype[key] = prop;
    }
}

extend({
    someOther: function () { console.log("someOther"); },
    someMore: function () { console.log("someMore"); }
});

var obj = new Afunction();
obj.vlog();
obj.someOther();
obj.someMore();

and output

some value
someOther
someMore

But in my VS Code show only the vlog in autocomplete suggestion. someOther and someOther not display there.

I learn about the extend function in jQuery. I try to implement it in my flavor. But I face this auto complete issue there are so many function property in my object so if autocompletion work it will be great. Otherwise I have to write all the property function Afunction.prototype.someOther like this.

I see there are so many .ts file in ESLint folder if there are any way to make a map/interface file, so I once add all props there and it show me suggestion.