An example of how to automatically surface a unique discount code based on someone's location using Cloudflare Workers. https://workers.cloudflare.com/

discount-code-api.js

// 
// This part goes on Cloudflare Workers
//

addEventListener('fetch', function (event) {
	event.respondWith(handleRequest(event.request));
});

/**
 * Available discounts
 */

var discounts = {
	US: {
		location: 'United States',
		locationCode: 'US',
		discountAmount: 15,
		discountCode: 'HIAMERICA',
	},
	CA: {
		location: 'Canada',
		locationCode: 'CA',
		discountAmount: 33,
		discountCode: 'HICANADA',
	},
	AU: {
		location: 'Australia',
		locationCode: 'AU',
		discountAmount: 42,
		discountCode: 'HIAUSTRALIA',
	}
};

/**
 * Respond to the request
 * @param {Request} request
 */
async function handleRequest(request) {

	let headers = new Headers({
		'Access-Control-Allow-Origin': '*',
		'Access-Control-Allow-Methods': 'GET, HEAD, POST, OPTIONS',
		'Access-Control-Allow-Headers': '*'
	});

	return new Response(JSON.stringify({
		discount: discounts[request.cf.country]
	}), {
		status: 200,
		headers: headers
	});

};

get-discount-code.js

//
// This part goes on your own website
//

var getLocation = function () {
	fetch('https://discounts.gomakethings.workers.dev').then(function (response) {
		if (response.ok) {
			return response.json();
		}
		return Promise.reject(response);
	}).then(function (data) {
		if (data.discount) {
			// Show a discount code somewhere
			// data is the discount details
		}
	}).catch(function(error) {

		// Log a warning for debugging
		console.warn(error);

	});
};