svrjs-nextjs-website/pages/docs/api/svrjs-api.md

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---
title: SVR.JS API (.js mods)
---
## SVR.JS API (_.js_ mods)
SVR.JS has its API for _.js_ mods that expands its functionality. SVR.JS API extends vanilla Node.JS HTTP API.
### Error handling
When a JavaScript error is thrown outside of event callbacks, SVR.JS will return a 500 error to the client. Inside event callbacks, SVR.JS will simply crash.
#### Incorrect Error Handling:
```js
//XXX WARNING!!! IT WILL CRASH THE SVR.JS!!!
//It also contains path traversal vulnerability!
module.exports = (req, res, logFacilities, config, next) => {
let headers = config.getCustomHeaders();
headers["Content-Type"] = "text/html; charset=utf8";
if (req.parsedURL.pathname == "/page.svr") {
fs.readFile(".template", (err, data) => {
if (err) throw err; //EVIL!!!
let id = req.parsedURL.query.id;
if (!id) id = "index";
if (fs.existsSync("pages/" + id + ".html")) {
fs.readFile("pages/" + id + ".html", (err2, data2) => {
if (err2) throw err2; //EVIL TWO!!!
res.writeHead(200, "OK", headers);
res.end(
data.toString().replace("{websiteContents}", data2.toString())
);
});
} else {
res.error(404);
}
});
} else if (href == "/") {
res.redirect("/page.svr");
} else {
next();
}
};
module.exports.modInfo = {
name: "Custom server-side JavaScript",
version: "0.0.0",
};
```
Instead, you should handle errors gracefully using `res.error` function:
#### Correct Error Handling:
```js
//Much better!
module.exports = (req, res, logFacilities, config, next) => {
let headers = config.getCustomHeaders();
headers["Content-Type"] = "text/html; charset=utf8";
if (req.parsedURL.pathname == "/page.svr") {
fs.readFile(".template", (err, data) => {
if (err) {
res.error(500, err);
return;
}
let id = req.parsedURL.query.id;
if (!id) id = "index";
id = id
.replace(/\\/g, "/")
.replace(/(?:\/|^)\.\.(?=(\/|$))/g, "$1")
.replace(/\/+/g, "/"); //Poor mans path sanitiation
if (fs.existsSync("pages/" + id + ".html")) {
fs.readFile("pages/" + id + ".html", (err2, data2) => {
if (err2) {
res.error(500, err2);
return;
}
res.writeHead(200, "OK", headers);
res.end(
data.toString().replace("{websiteContents}", data2.toString())
);
});
} else {
res.error(404);
}
});
} else if (href == "/") {
res.redirect("/page.svr");
} else {
next();
}
};
module.exports.modInfo = {
name: "Custom server-side JavaScript",
version: "0.0.0",
};
```
By using `res.error`, you can handle errors effectively and provide appropriate error responses to the client, preventing SVR.JS from crashing due to unhandled exceptions.
### Main callback API (`module.exports`)
<small>_Added in SVR.JS 4.0.0_</small>
This API includes proxy requests, which don't use CONNECT method. It's possible to determine, if the request comes from the proxy with `req.isProxy` property.
SVR.JS applies mods for request URLs beginning with "_http://_" or with "_https://_" (proxy through GET or POST method, non-proxy requests have request URLs beginning with "_/_") only if _module.exports.proxy_ method is present or if _module.exports.proxySafe_ property is set to `true`.
#### _req_
<small>_Added in SVR.JS 4.0.0_</small>
_req_ object is almost same, as _req_ object in Node.JS
#### _req.socket.realRemoteAddress_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing IP address, from which request originally went from, if request is sent through reverse proxy.
You can specify generic request IP variable using `const reqip = req.socket.realRemoteAddress ? req.socket.realRemoteAddress : req.socket.remoteAddress`
#### _req.socket.realRemotePort_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing port number, from which request originally went from, if request is sent through reverse proxy. (for _X-Forwarded-For_ header, it will be _null_)
You can specify generic request IP variable using `const reqip = req.socket.realRemotePort ? req.socket.realRemotePort : req.socket.remotePort`
#### _req.socket.originalRemoteAddress_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing IP address, from which proxy request came from. If the request isn't a proxy request, it will be `undefined`.
#### _req.socket.originalRemotePort_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing port number, from which proxy request came from. If the request isn't a proxy request, it will be `undefined`.
#### _req.url_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing request URL after all processing (URL rewriting too).
#### _req.parsedURL_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing parsed request URL created by a custom URL parser (compatible with legacy URL parser: `url.parse()`)
#### _req.originalParsedURL_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing parsed request URL (before URL rewriting) created by a custom URL parser (compatible with legacy URL parser: `url.parse()`)
#### _req.isProxy_
<small>_Added in SVR.JS 4.0.0_</small>
A property that determines if request is a proxy request or not.
#### _req.authUser_
<small>_Added in SVR.JS 4.0.0_</small>
The name of authenticated HTTP user. If the user wasn't authenticated, the property would be _null_.
#### _res_
<small>_Added in SVR.JS 4.0.0_</small>
_res_ object is almost same, as _res_ object in Node.JS
#### _res.socket.realRemoteAddress_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing IP address, from which request originally went from, if request is sent through reverse proxy.
You can specify generic request IP variable using `const reqip = req.socket.realRemoteAddress ? req.socket.realRemoteAddress : req.socket.remoteAddress`
#### _res.socket.realRemotePort_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing port number, from which request originally went from, if request is sent through reverse proxy. (for _X-Forwarded-For_ header, it will be _null_)
You can specify generic request IP variable using `const reqip = req.socket.realRemotePort ? req.socket.realRemotePort : req.socket.remotePort`
#### _res.socket.originalRemoteAddress_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing IP address, from which proxy request came from. If the request isn't a proxy request, it will be `undefined`.
#### _res.socket.originalRemotePort_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing port number, from which proxy request came from. If the request isn't a proxy request, it will be `undefined`.
#### _res.writeHead(statusCode[, statusMessage][, headers])_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _statusCode_ - the response status code (_String_)
- _statusMessage_ - the response status message (optional; _String_)
- _headers_ - the response headers (optional; _Object_)
Returns: _res_ property.
The difference between _res.writeHead_ in Node.JS, and in SVR.JS is that in SVR.JS it writes into server log, doesn't invoke a warning about unused status code string, and if called multiple times will emit a warning, instead of throwing an error, which could crash SVR.JS.
#### _res.setHeader(name, value)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _name_ - the response header name (_String_)
- _value_ - the response header value (optional; _String_ or _Array_)
The difference between _res.setHeader_ in Node.JS, and in SVR.JS is that in SVR.JS it doesn't invoke a warning about HTTP/1.x headers being not allowed in HTTP/2.
Custom headers defined in _config.json_ are set by default.
#### _res.head_
<small>_Added in SVR.JS 4.0.0_</small>
HTML head read from either _.head_ or _head.html_ file.
#### _res.foot_
<small>_Added in SVR.JS 4.0.0_</small>
HTML foot read from either _.foot_ or _foot.html_ file.
#### _res.responseEnd(body)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _body_ - message you want to send before ending response (_String_ or _Buffer_)
Sends response message (along with custom head and foot) specified by _body_ parameter.
#### _res.error(errorCode[, extName][, stack][, ch])_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _errorCode_ - HTTP error code (_Number_)
- _extName_ - extension name, which caused an error (optional; _String_)
- _stack_ - error stack (optional; _String_ or _Error_)
- _ch_ - custom HTTP headers for error (optional; _Object_)
Invokes HTTP error code. If it's unavailable, invokes 501 error code.
#### _res.redirect(dest[, isTemporary][, keepMethod][, headers])_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _dest_ - destination of redirect (_String_)
- _isTemporary_ - if _true_, then redirect with 302 code. Else redirect with 301 code. When _keepMethod_ parameter is set to _true_, then redirect with 307 code, when _isTemporary_ is true or with 308 code otherwise. (optional; _Boolean_)
- _keepMethod_ - if _true_, then redirect with either 307 or 308 code. Else redirect with etiher 301 or 302 code. (optional; _Boolean_; SVR.JS 3.13.0 or later)
- _headers_ - custom HTTP headers for redirect (optional; _Object_)
Redirects HTTP client to specific destination.
#### _logFacilities_
<small>_Added in SVR.JS 4.0.0_</small>
The log facilities for SVR.JS.
#### _logFacilities.climessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends CLI message to server console.
#### _logFacilities.reqmessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends request message to server console.
#### _logFacilities.resmessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends response message to server console.
#### _logFacilities.errmessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends response error message to server console.
#### _logFacilities.locerrmessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends local error message to server console.
#### _logFacilities.locwarnmessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends local warning message to server console.
#### _logFacilities.locmessage(message)_
<small>_Added in SVR.JS 4.0.0_</small>
Parameters:
- _message_ - message you want to send to server console (_String_)
Sends local message to server console.
#### _config_
<small>_Added in SVR.JS 4.0.0_</small>
This object contains properties from _config.json_ file.
#### _config.getCustomHeaders()_
<small>_Added in SVR.JS 4.0.0_</small>
Returns: _Object_ property contains custom headers.
This methods retrieves custom headers from _config.json_ file. Returned object additionally includes _Server_ header.
#### _config.generateServerString()_
<small>_Added in SVR.JS 4.0.0_</small>
Returns: The generated server string.
This methods generated the string which is used to identify a web server (the same string as in the "Server" header).
#### _next()_
<small>_Added in SVR.JS 4.0.0_</small>
Invokes next SVR.JS mod callback, SVR.JS server-side JavaScript callback or main SVR.JS callback.
### Proxy callback API (`module.exports.proxy`)
<small>_Added in SVR.JS 4.0.0_</small>
#### _req_
<small>_Added in SVR.JS 4.0.0_</small>
_req_ object is the same, as _req_ object in Node.JS
#### _socket_
<small>_Added in SVR.JS 4.0.0_</small>
_socket_ object is the same, as _socket_ object in Node.JS
#### _head_
<small>_Added in SVR.JS 4.0.0_</small>
_head_ object is the same, as _head_ object in Node.JS
#### _logFacilities_
<small>_Added in SVR.JS 4.0.0_</small>
_See logFacilties in main callback API_
#### _config_
<small>_Added in SVR.JS 4.0.0_</small>
_See config in main callback API_
#### _next()_
<small>_Added in SVR.JS 4.0.0_</small>
_See next in main callback API_
### Global variables (for use in callback APIs)
#### _process.versions.svrjs_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing SVR.JS version.
#### _process.serverConfiguration_
<small>_Added in SVR.JS 4.0.0_</small>
A property containing SVR.JS configuration from _config.json_ file.
#### _process.dirname_
<small>_Added in SVR.JS 4.0.0_</small>
A property containg the SVR.JS installation directory.
#### _process.filename_
<small>_Added in SVR.JS 4.0.0_</small>
A property containg the path to the SVR.JS script.
#### _process.err4xxcounter_
<small>_Added in SVR.JS 4.0.0_</small>
A property containg the count of 4xx HTTP errors.
#### _process.err5xxcounter_
<small>_Added in SVR.JS 4.0.0_</small>
A property containg the count of 5xx HTTP errors.
#### _process.reqcounter_
<small>_Added in SVR.JS 4.0.0_</small>
A property containg the count of HTTP requests.
#### _process.malformedcounter_
<small>_Added in SVR.JS 4.0.0_</small>
A property containg the count of malformed HTTP requests.