A simple validation method to validate given user inputs for address

validator.js

export default class Delivery extends Component {

  state = {
    streetName: undefined,
    postcode: undefined,
    city: undefined
  };

  constructor(props) {
    super(props);
    this._postcodeEntry = undefined;
    this._addressEntry = undefined;
    this._cityEntry = undefined;
  }

  validateAndSetAttribute(key, value) {

      // Ideally these should be declared in constants.js file
      const postcodeRegex = /([Gg][Ii][Rr] 0[Aa]{2})|((([A-Za-z][0-9]{1,2})|(([A-Za-z][A-Ha-hJ-Yj-y][0-9]{1,2})|(([A-Za-z][0-9][A-Za-z])|([A-Za-z][A-Ha-hJ-Yj-y][0-9]?[A-Za-z]))))\s?[0-9][A-Za-z]{2})/;
      const addressRegex = /^(\d{0,3}[0–9])(\s\w{1,}[A-Za-z])+/;
      const cityRegex = /^(\w[A-Za-z ]{2,57})/;

      this.setState({ key: value });

      let borderColor;
      switch (key) {

        case "postcode":
          borderColor = value.match(postcodeRegex) === null ? "red" : "white";
          this._postcodeEntry.setNativeProps({
            style: { borderColor }
          });
          break;

        case "streetName":
          borderColor = value.match(addressRegex) === null ? "red" : "white";
          this._addressEntry.setNativeProps({
            style: { borderColor }
          });
          break;

        case "city":
          borderColor = value.match(cityRegex) === null ? "red" : "white";
          this._cityEntry.setNativeProps({
            style: { borderColor }
          });
          break;

      }
    }
  }