Lit Example: Simple

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import { LitElement, html, nothing } from 'lit'
import { customElement } from 'lit/decorators.js'

import { TanStackFormController } from '@tanstack/lit-form'
import { repeat } from 'lit/directives/repeat.js'

@customElement('tanstack-form-demo')
export class TanStackFormDemo extends LitElement {
  #form = new TanStackFormController(this, {
    defaultValues: {
      firstName: '',
      lastName: '',
    },
    onSubmit({ value }) {
      // Do something with form data
      console.log(value)
    },
  })

  render() {
    return html`
      <form
        @submit=${(e: Event) => {
          e.preventDefault()
          e.stopPropagation()
          this.#form.api.handleSubmit()
        }}
      >
          ${this.#form.field(
            {
              name: `firstName`,
              validators: {
                onChange: ({ value }) =>
                  !value
                    ? 'A first name is required'
                    : value.length < 3
                      ? 'First name must be at least 3 characters'
                      : undefined,
                onChangeAsyncDebounceMs: 500,
                onChangeAsync: async ({ value }) => {
                  await new Promise((resolve) => setTimeout(resolve, 1000))
                  return (
                    value.includes('error') &&
                    'No "error" allowed in first name'
                  )
                },
              },
            },
            (field) => {
              return html` <div>
                <label for="${field.name}">First Name:</label>
                <input
                  id="${field.name}"
                  name="${field.name}"
                  .value="${field.state.value}"
                  @blur="${() => field.handleBlur()}"
                  @input="${(e: Event) => {
                    const target = e.target as HTMLInputElement
                    field.handleChange(target.value)
                  }}"
                />
                ${field.state.meta.isTouched && !field.state.meta.isValid
                  ? html`${repeat(
                      field.state.meta.errors,
                      (__, idx) => idx,
                      (error) => {
                        return html`<div style="color: red;">${error}</div>`
                      },
                    )}`
                  : nothing}
                ${field.state.meta.isValidating
                  ? html`<p>Validating...</p>`
                  : nothing}
              </div>`
            },
          )}
        </div>
        <div>
          ${this.#form.field(
            {
              name: `lastName`,
            },
            (field) => {
              return html` <div>
                <label for="${field.name}">Last Name:</label>
                <input
                  id="${field.name}"
                  name="${field.name}"
                  .value="${field.state.value}"
                  @blur="${() => field.handleBlur()}"
                  @input="${(e: Event) => {
                    const target = e.target as HTMLInputElement
                    field.handleChange(target.value)
                  }}"
                />
              </div>`
            },
          )}
        </div>

        <button type="submit" ?disabled=${this.#form.api.state.isSubmitting}>
          ${this.#form.api.state.isSubmitting ? '...' : 'Submit'}
        </button>
        <button
          type="button"
          @click=${() => {
            this.#form.api.reset()
          }}
        >
          Reset
        </button>
      </form>
    `
  }
}

import { LitElement, html, nothing } from 'lit'
import { customElement } from 'lit/decorators.js'

import { TanStackFormController } from '@tanstack/lit-form'
import { repeat } from 'lit/directives/repeat.js'

@customElement('tanstack-form-demo')
export class TanStackFormDemo extends LitElement {
  #form = new TanStackFormController(this, {
    defaultValues: {
      firstName: '',
      lastName: '',
    },
    onSubmit({ value }) {
      // Do something with form data
      console.log(value)
    },
  })

  render() {
    return html`
      <form
        @submit=${(e: Event) => {
          e.preventDefault()
          e.stopPropagation()
          this.#form.api.handleSubmit()
        }}
      >
          ${this.#form.field(
            {
              name: `firstName`,
              validators: {
                onChange: ({ value }) =>
                  !value
                    ? 'A first name is required'
                    : value.length < 3
                      ? 'First name must be at least 3 characters'
                      : undefined,
                onChangeAsyncDebounceMs: 500,
                onChangeAsync: async ({ value }) => {
                  await new Promise((resolve) => setTimeout(resolve, 1000))
                  return (
                    value.includes('error') &&
                    'No "error" allowed in first name'
                  )
                },
              },
            },
            (field) => {
              return html` <div>
                <label for="${field.name}">First Name:</label>
                <input
                  id="${field.name}"
                  name="${field.name}"
                  .value="${field.state.value}"
                  @blur="${() => field.handleBlur()}"
                  @input="${(e: Event) => {
                    const target = e.target as HTMLInputElement
                    field.handleChange(target.value)
                  }}"
                />
                ${field.state.meta.isTouched && !field.state.meta.isValid
                  ? html`${repeat(
                      field.state.meta.errors,
                      (__, idx) => idx,
                      (error) => {
                        return html`<div style="color: red;">${error}</div>`
                      },
                    )}`
                  : nothing}
                ${field.state.meta.isValidating
                  ? html`<p>Validating...</p>`
                  : nothing}
              </div>`
            },
          )}
        </div>
        <div>
          ${this.#form.field(
            {
              name: `lastName`,
            },
            (field) => {
              return html` <div>
                <label for="${field.name}">Last Name:</label>
                <input
                  id="${field.name}"
                  name="${field.name}"
                  .value="${field.state.value}"
                  @blur="${() => field.handleBlur()}"
                  @input="${(e: Event) => {
                    const target = e.target as HTMLInputElement
                    field.handleChange(target.value)
                  }}"
                />
              </div>`
            },
          )}
        </div>

        <button type="submit" ?disabled=${this.#form.api.state.isSubmitting}>
          ${this.#form.api.state.isSubmitting ? '...' : 'Submit'}
        </button>
        <button
          type="button"
          @click=${() => {
            this.#form.api.reset()
          }}
        >
          Reset
        </button>
      </form>
    `
  }
}