[krutoy]

devote,
Вот так, кажись, можно

Object.prototype.inherit=function(parent){
    var o = Object.create(parent.prototype)
    o.constructor=this.prototype.constructor
    this.prototype=o
}

function FormField(data) {
  this._d = data;
}
    
function FormFile(data, opts) {
  FormField.call(this, data);
  this.opts = opts;
}
    
FormFile.inherit(FormField)
    
o=new FormField()
console.log(o.constructor); // [Function: FormField]
 
o=new FormFile()
console.log(o.constructor); // [Function: FormFile]