src/fields/Width.php
public function getSettingsHtml()
    {
        // Register our asset bundle
        Craft::$app->getView()->registerAssetBundle(WidthFieldtypeAsset::class);

        // Get our id and namespace
        $id = Craft::$app->getView()->formatInputId('width-fieldtype');
        $namespacedId = Craft::$app->getView()->namespaceInputId($id);

        Craft::$app->getView()->registerJs("new WidthSelectInput('{$namespacedId}');");

        // Render the settings template
        return Craft::$app->getView()->renderTemplate(
            'width-fieldtype/_components/fields/Width_settings',
            [
                'field'        => $this,
                'allOptions'   => array_keys(self::getOptions()),
                'id'           => $id,
                'namespacedId' => $namespacedId,
                'settings'     => $this->settings,
            ]
        );
    }
public function getSettingsHtml()
    {
        // Register our asset bundle
        Craft::$app->getView()->registerAssetBundle(WidthFieldtypeAsset::class);

        // Get our id and namespace
        $id = Craft::$app->getView()->formatInputId('width-fieldtype');
        $namespacedId = Craft::$app->getView()->namespaceInputId($id);

        Craft::$app->getView()->registerJs("new WidthSelectInput('{$namespacedId}');");

        // Render the settings template
        return Craft::$app->getView()->renderTemplate(
            'width-fieldtype/_components/fields/Width_settings',
            [
                'field'        => $this,
                'allOptions'   => array_keys(self::getOptions()),
                'id'           => $id,
                'namespacedId' => $namespacedId,
                'settings'     => $this->settings,
            ]
        );
    }
Returns the component’s settings HTML.

@throws \Twig_Error_Loader
@throws \yii\base\Exception

@return string|null