dedupe.js

// Install lodash and airtable with npm or yarn
const _ = require('lodash');
const Airtable = require('airtable');

// Get API key and base ID from https://airtable.com/api
const base = new Airtable({apiKey: 'YOUR_API_KEY'}).base('YOUR_BASE_ID');

// Fill in your table and field names.
const tableName = 'Table 1';
const emailField = 'Email';
const createdTimeField = 'Created time';
const fieldsToMerge = ['Notes', 'Rating'];

base(tableName).select().all().then(async allRecords => {
    // Sort by created time ascending
    allRecords = _.sortBy(allRecords, record => record.get(createdTimeField));

    // Group by email address
    const recordsByEmail = _.groupBy(allRecords, record => record.get(emailField));

    for (const records of Object.values(recordsByEmail)) {
        if (records.length === 1) {
            // No dupes.
            continue;
        }

        // Merge into the oldest record.
        const cellValuesByField = {};
        for (const field of fieldsToMerge) {
            for (const record of records) {
                const cellValue = record.get(field);
                if (cellValue) {
                    // Ignore empty cells.
                    cellValuesByField[field] = cellValue;
                }
            }

        }
        await records[0].patchUpdate(cellValuesByField);

        // Delete other records.
        for (let i = 1; i < records.length; i++) {
            await records[i].destroy();
        }
    }
});