copy-field-data-other-field/copy-field-data.html

<!doctype html>
<html>

<head>
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <script src="https://unpkg.com/@contentstack/ui-extensions-sdk@2.2.0/dist/ui-extension-sdk.js"></script>
    <link href="https://www.contentstack.com/sdks/contentstack-ui-extensions/dist/latest/ui-extension-sdk.css"
        rel="stylesheet" type="text/css" media="all">
</head>

<body>
    <div>
        <div class="cs-checkbox">
            <label style="margin:10px">
                <input type="checkbox" class="cs" onchange="HandleChange(this)">
                <span class="lbl"></span>
            </label>
        </div>

    </div>
    <script>
        // initialise Field Extension
        window.extensionField = {};
        ContentstackUIExtension.init().then(function (extension) {
            // make extension object globally available
            extensionField = extension;
            extensionField.window.updateHeight();
        })
        function HandleChange(checkbox) {
            if (checkbox.checked == true) {
                var fromFieldData = extensionField.entry._changedData[extensionField.fieldConfig.from];
                var toField = extensionField.entry.getField(extensionField.fieldConfig.to);
                toField.setData(fromFieldData)

            } else {
                // uncheck functionality
            }
        }
    </script>
</body>
</html>