Typescript Class-Validator for property of class

Question

I was trying to use the class-validator decorator library for the validation processes . So, I was implemented on my sample project. But, it is not working. The sample project is trying to create sample projects with user inputs and I am trying to check those inputs(example on my code I am trying to validate contains of title with that class-validator. But, decorators are executing before the set of value of input elements. So, the title looks empty all time, and validation fails.

What I am missing? How can I use that library for valid to upcoming value from inputs?

My app.ts = >

import { validate, Contains } from "class-validator";

class ProjectInput {
  templateElement: HTMLTemplateElement;
  hostElement: HTMLDivElement;
  formElement: HTMLFormElement;

  @Contains("hello")
  titleInputElement: HTMLInputElement;

  descriptionInputElement: HTMLInputElement;
  peopleInputElement: HTMLInputElement;

  constructor() {
    this.templateElement = <HTMLTemplateElement>(
      document.getElementById("project-input")!
    );
    this.hostElement = <HTMLDivElement>document.getElementById("app")!;
    const importedNode = document.importNode(
      this.templateElement.content,
      true
    );
    this.formElement = <HTMLFormElement>importedNode.firstElementChild;
    this.formElement.id = "user-input";

    this.titleInputElement = <HTMLInputElement>(
      this.formElement.querySelector("#title")
    );

    this.descriptionInputElement = <HTMLInputElement>(
      document.getElementById("description")
    );

    this.peopleInputElement = <HTMLInputElement>(
      document.getElementById("people")
    );
    this.configure();
    this.attach();
  }

  private submitHandler(event: Event) {
    event.preventDefault();
    console.log(this.titleInputElement.value);
  }

  private configure() {
    this.formElement.addEventListener("submit", this.submitHandler.bind(this));
  }
  private attach() {
    this.hostElement.insertAdjacentElement("afterbegin", this.formElement);
  }
}

const prjInputExample = new ProjectInput();
validate(prjInputExample).then((errors) => {
  // errors is an array of validation errors
  if (errors.length > 0) {
    console.log("validation failed. errors: ", errors);
  } else {
    console.log("validation succeed");
  }
});

index.html =>

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>ProjectManager</title>
    <link rel="stylesheet" href="app.css" />
    <script src="bundles/bundle.js" defer></script>
  </head>
  <body>
    <template id="project-input">
      <form>
        <div class="form-control">
          <label for="title">Title</label>
          <input type="text" id="title" />
        </div>
        <div class="form-control">
          <label for="description">Description</label>
          <textarea id="description" rows="3"></textarea>
        </div>
        <div class="form-control">
          <label for="people">People</label>
          <input type="number" id="people" step="1" min="0" max="10" />
        </div>
        <button type="submit">ADD PROJECT</button>
      </form>
    </template>
    <template id="single-project">
      <li></li>
    </template>
    <template id="project-list">
      <section class="projects">
        <header>
          <h2></h2>
        </header>
        <ul></ul>
      </section>
    </template>
    <div id="app"></div>
  </body>
</html>

Michał Lis · Accepted Answer · 2021-05-09 10:41:24Z

1

You placed validate method just inside app.ts script. It is invoked when the script is executed, so at the page load. If I understand you well you want to make validation when user type in another character into titleInputElement. You can achieve it via

@Contains('hello')
titleValue: string;

titleInputElement.addEventListener('input', event => {
    this.titleValue = this.titleInputElement.value;
    validate(this);
})

Worth to mention that you need to validate other property than titleInputElement: HTMLElement. As docs says:

@Contains(seed: string) Checks if the string contains the seed.

So it's gotta be string property (in my example it's titleValue)

edited May 9, 2021 at 10:41

answered May 6, 2021 at 10:32

Michał Lis

5611 gold badge6 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Cihat Şaman Over a year ago

I want to make validation with using the class-validator library when the title contains a specific string as above example "hello". I tried to use your code but it didn't work for me or still, I am missing something.

Michał Lis Over a year ago

I've edited my post. I've missed that titleInputElement type is not suitable with @Contains.

Cihat Şaman Over a year ago

I am getting that error :Property 'value' does not exist on type 'EventTarget. If you could clone the project and if you could to try it from your side I would appreciate it . The repo's link

Michał Lis Over a year ago

this.titleValue = this.titleInputElement.value; should do better

Collectives™ on Stack Overflow

Typescript Class-Validator for property of class

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related