Magento 2 - Add success message with knockout

Question

I need add an errorMessage or successMessage on checkout/cart after an jquery validation. I tried require file 'Magento_Ui/js/model/messageList' for this but not have success.

My code:

define(
    [
        'jquery',
        'Magento_Ui/js/model/messageList'
    ],
    function ($, messageList) {
       $.ajax({
           type: "GET",
           url: /route/controller,
           async: false,
           success: function (res) {
               if (res.val) {
                  messageList.addErrorMessage({'message': messageError});
               }
           }
       });
    }
);

Answer 1

I'm not sure if you already solved this or not, but here it goes anyway. While Rakesh might be right (a controller is the preferred way), it doesn't answer the question. I found the easiest way of doing this is through the customerData object:

customerData.set('messages', {
    messages: [{
        type: 'success',
        text: 'Hello World'
    }]
});

Answer 2

I did this approach for after page load message display:

     define(['uiRegistry', 'mage/translate'], function(uiRegistry, $t) {
         let msgComponent = uiRegistry.get('index = messages');
         msgComponent.messages().messages = [];
         msgComponent.messages().messages.push({
            type: 'warning',
            text: $t('You are not allowed to edit this user.')
          });
         msgComponent.messages.valueHasMutated();
     });

You can use type as 'error', 'warning', 'success', etc...

Answer 3

Add success message in your controller it will automatically display in your page.