Data Validation using Decorator in Typescript

In index.html we have

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<form>   <input type="text" placeholder="Course Title" id="title" />   <input type="text" placeholder="Price" id="price" />   <button type="submit">Submit</button> </form>

and inside our ts (transpiled into js file and link it into our index.html), we write:

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enum Validation {   required = "required",   positive = "positive" }   interface ValidatorConfig {   [property: string]: {     [validatableProp: string]: Validation[]; //e.g., [Validation.required, Validation.positive]   }; }   const registeredValidators: ValidatorConfig = {};   function Required(target: any, propName: string) {   //we don't have propertyDescriptor for property, it exists only for methods   registeredValidators[target.constructor.name] = {     ...registeredValidators[target.constructor.name],     [propName]: [Validation.required]   }; }   function Positive(target: any, propName: string) {   registeredValidators[target.constructor.name] = {     ...registeredValidators[target.constructor.name],     [propName]: [Validation.positive]   }; }   function validate(obj: any) {   const objValidatorConfig = registeredValidators[obj.constructor.name];   if (!objValidatorConfig) {     return true;   } else {     let validated = true;     for (const prop in objValidatorConfig) {       for (const validator of objValidatorConfig[prop]) {         if (validator === (Validation.required as string)) {           console.log("run?");           validated = validated && obj[prop].trim().length > 0;         }         if (validator === (Validation.positive as string)) {           validated = validated && obj[prop] > 0;         }       }     }     return validated;   } }   class Course {   @Required   public title: string;     @Positive   public price: number;     constructor(t: string, p: number) {     this.title = t;     this.price = p;   } }   const courseForm = document.querySelector("form")!; courseForm.addEventListener("submit", e => {   e.preventDefault();   const titleEl = document.getElementById("title") as HTMLInputElement;   const priceEl = document.getElementById("price") as HTMLInputElement;   const title = titleEl.value;   const price = +priceEl.value;   const newCourse = new Course(title, price);     if (!validate(newCourse)) {     alert("Invalid input, please try again!");     return;   }     console.log(newCourse); });