Javascript assign function to existing variable

I think you want something like bellow:-

var someVar = {};
someVar.text = "some text";

var thisFunc = function(){
  //do some
}
someVar.func = thisFunc;

It seems that an extend function would come in handy in your situation. It's a little helper function, that assigns properties of one object to another one (if you are using a third party library like Underscore, you might already have such a function available):

function extend(obj1, obj2) {
    for (var key in obj2) {
        if (Object.prototype.hasOwnProperty.call(obj2, key)) {
            obj1[key] = obj2[key];
        }
    }
    return obj1;
}

Then you can do:

var someVar = {};
someVar.text = "some text";

var thisFunc = function(){
    this.subfunc = function(){

    }
}

someVar = extend(thisFunc, someVar);