How to check for props?

Question

Vue.js

Good day, comrades. Tell the young and green. I use validation in vuetify, on the submit button:

this.formHasErrors = false;
Object.keys(this.form).forEach(f => {
  if(!this.form[f]){
    this.formHasErrors = true;
    this.$refs[f].validate(true);
  }
})

this.$refs doesn't always have a validate prop, but when it doesn't, there is a ref inside that has that prop. How can you take the validate of an internal ref if the one being checked does not have it?