svrjs-nextjs-website/pages/docs/server-side-javascript/migration.md

title
Migration to SVR.JS

Migration to SVR.JS

If you have previously built your web application using the Node.JS http library, Express framework, or Koa framework, you can easily migrate that code to SVR.JS server-side JavaScript.

From Node.JS http library

For applications built with the Node.JS http library, you can simply copy the contents of the request event listener to the SVR.JS server-side JavaScript. However, make sure to consider the disableEndElseCallbackExecute option to ensure proper execution flow.

disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!

// Node.JS http library request event listener code goes here.
if (req.url == "/" && req.method == "GET") {
	res.writeHead(200, "OK", {
		"Content-Type": "text/plain",
	});
	res.end("Hello World!");
	return;
}

elseCallback(); // Optionally, invoke main SVR.JS callback.

From Express Framework

If your application is built using the Express framework, you can easily migrate it to SVR.JS. You can mix Express methods with SVR.JS methods for more flexibility.

disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!

var express = require("express");
// Other requires go here.

var app = express(); // Initialize express app

// Express application code goes here!
app.get("/", function (req, res) {
	res.send("Hello World!");
});

app.use(elseCallback); // Optionally, if you want the main SVR.JS callback.

app(req, res); // Invoke Express handler

From Koa Framework

Migrating from the Koa framework to SVR.JS is also straightforward. Here's an example of how you can do it:

disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!

var koa = require("koa");
// Other requires go here.

var app = new koa(); // Initialize Koa app

// Koa application code goes here!
app.use(function (ctx, next) {
	if (ctx.method != "GET" || ctx.path != "/") {
		next(); // Koa router could be used...
	} else {
		ctx.body = "Hello World!";
	}
});

// Optionally, if you want the main SVR.JS callback (not recommended by Koa, as it passes Node.JS req and res objects).
app.use(function (ctx) {
	ctx.respond = false;
	elseCallback(ctx.req, ctx.res);
});

app.callback()(req, res); // Invoke Koa handler

By migrating your web application to SVR.JS, you can take advantage of its features and performance enhancements, while still preserving your existing codebase.

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