type-definitions/src/String.js

Define and validate types in js

import { BaseType } from './base';
import nativeTypeMap from './nativeTypeMap';

export default class StringType extends BaseType {
  static isOfType(val) {
    return typeof val === 'string';
  }
  static get defaultValue() {
    return "";
  }
}

nativeTypeMap.set(String, StringType);