How to redirect a customer to a custom payment gateway after he has clicked on "Place Order"?

Ask your questions
1

Hello,

I used PayPal payment function to redirect customers to custom payment gateway but after click on “Place Order” then I get js error
This is my function :

// Redirect to gateway
placeOrder: function () {
    this.selectPaymentMethod();
    setPaymentMethodAction(this.messageContainer).done(
        function () {
            $.mage.redirect(
                window.checkoutConfig.payment.gateway.redirectUrl[quote.paymentMethod().method]
            );
        }
    );
    return false;
}

And this is error after click:

TypeError: Cannot read property 'done' of undefined
/magento2/pub/static/frontend/Magento/luma/....../js/view/payment/method-renderer/gateway-method.js:93