framework/validators/RegularExpressionValidator.php
public function getClientOptions($model, $attribute)
    {
        $pattern = Html::escapeJsRegularExpression($this->pattern);

        $options = [
            'pattern' => new JsExpression($pattern),
            'not' => $this->not,
            'message' => $this->formatMessage($this->message, [
                'attribute' => $model->getAttributeLabel($attribute),
            ]),
        ];
        if ($this->skipOnEmpty) {
            $options['skipOnEmpty'] = 1;
        }

        return $options;
    }
public function getClientOptions($model, $attribute)
    {
        $pattern = Html::escapeJsRegularExpression($this->pattern);

        $options = [
            'pattern' => new JsExpression($pattern),
            'not' => $this->not,
            'message' => $this->formatMessage($this->message, [
                'attribute' => $model->getAttributeLabel($attribute),
            ]),
        ];
        if ($this->skipOnEmpty) {
            $options['skipOnEmpty'] = 1;
        }

        return $options;
    }
{@inheritdoc}