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Polymer Forms — Input Validation, Custom Form Elements, and Form Association

DodaTech Updated 2026-06-29 1 min read

In this tutorial, you will learn about Polymer Forms. We cover key concepts, practical examples, and best practices to help you master this topic.

Polymer supports creating custom form elements that participate in HTML form submission and validation, extending the browser's built-in form capabilities.

<dom-module id="validated-input">
  <template>
    <input id="input" value="{{value::input}}" required$="{{required}}">
    <span class="error" hidden$="{{!invalid}}">{{errorMessage}}</span>
  </template>
  <script>
    class ValidatedInput extends Polymer.Element {
      static get is() { return 'validated-input'; }
      static get properties() {
        return {
          value: { type: String, notify: true },
          required: { type: Boolean, value: false },
          invalid: { type: Boolean, value: false }
        };
      }
      checkValidity() {
        if (this.required && !this.value) {
          this.invalid = true;
          return false;
        }
        this.invalid = false;
        return true;
      }
    }
  </script>
</dom-module>

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