How to stop Kintone from saving duplicate records in the Create Record page?

I want to prevent users from saving duplicate company records in the database. So in the app.record.create.submit event handler, I call checkDuplicate(record)  to check to see if the company record already exists. The checkDuplicate(record) is a function that calls a kintone.proxy() 

The kintone.proxy() is an asynchronous operation.

The problem is the event handler app.record.create.submit finishes before kintone.proxy() finishes and the duplicate record is saved.

How to stop the user from saving a duplicate company record?

// This event is triggered when the SAVE button is clicked on the record create page.“app.record.create.submit”, function (event) {

        var record = event.record;


        return event;


Hello annaylee,


Before we look deeper into this, I just want to make sure if the Prohibit Duplicate Values setting, a native feature available in many fields, does not meet your operation here?