serialized preloaded data and send to client as initial payload - fixes #3

lib/index.js

@@ -1,5 +1,6 @@
 const fs = require('fs');
 const path = require('path');
+const serialize = require('serialize-javascript');
 const route_manager = require('./route_manager.js');
 const templates = require('./templates.js');
 const create_app = require('./utils/create_app.js');
@@ -144,15 +145,25 @@ function get_route_handler(fn) {
 
 			if (mod.preload) {
 				const promise = Promise.resolve(mod.preload(req)).then(preloaded => {
+					const serialized = try_serialize(preloaded);
 					Object.assign(data, preloaded);
-					return mod.render(data);
+
+					return { rendered: mod.render(data), serialized };
 				});
 
 				return templates.stream(res, 200, {
-					scripts: `<script src='${client.main_file}'></script>`,
-					html: promise.then(rendered => rendered.html),
-					head: promise.then(({ head }) => `<noscript id='sapper-head-start'></noscript>${head}<noscript id='sapper-head-end'></noscript>`),
-					styles: promise.then(({ css }) => (css && css.code ? `<style>${css.code}</style>` : ''))
+					scripts: promise.then(({ serialized }) => {
+						const main = `<script src='${client.main_file}'></script>`;
+
+						if (serialized) {
+							return `<script>__SAPPER__ = { preloaded: ${serialized} };</script>${main}`;
+						}
+
+						return main;
+					}),
+					html: promise.then(({ rendered }) => rendered.html),
+					head: promise.then(({ rendered }) => `<noscript id='sapper-head-start'></noscript>${rendered.head}<noscript id='sapper-head-end'></noscript>`),
+					styles: promise.then(({ rendered }) => (rendered.css && rendered.css.code ? `<style>${rendered.css.code}</style>` : ''))
 				});
 			} else {
 				const { html, head, css } = mod.render(data);
@@ -249,4 +260,12 @@ function compose_handlers(handlers) {
 
 function read_json(file) {
 	return JSON.parse(fs.readFileSync(file, 'utf-8'));
+}
+
+function try_serialize(data) {
+	try {
+		return serialize(data);
+	} catch (err) {
+		return null;
+	}
 }