svrjs-nextjs-website/pages/docs/Api/svrjs-api-v2.mdx
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2024-09-06 23:06:08 +05:30

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## SVR.JS API (_.tar.gz_ mods and server-side JavaScript)
SVR.JS has its API for both _.tar.gz_ mods and server-side JavaScript 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!
disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!
var headers = getCustomHeaders();
headers["Content-Type"] = "text/html; charset=utf8";
if (href == "/page.svr") {
fs.readFile(".template", function (err, data) {
if (err) throw err; //EVIL!!!
var id = uobject.query.id;
if (!id) id = "index";
if (fs.existsSync("pages/" + id + ".html")) {
fs.readFile("pages/" + id + ".html", function (err2, data2) {
if (err2) throw err2; //EVIL TWO!!!
res.writeHead(200, "OK", headers);
res.end(data.toString().replace("{websiteContents}", data2.toString()));
});
} else {
callServerError(404);
}
});
} else if (href == "/") {
redirect("/page.svr");
} else {
elseCallback();
}
```
Instead, you should handle errors gracefully using _callServerError_ function:
#### Correct Error Handling:
```js
//Much better!
disableEndElseCallbackExecute = true; //Without "var", else it will not work!!!
var headers = getCustomHeaders();
headers["Content-Type"] = "text/html; charset=utf8";
if (href == "/page.svr") {
if (fs.existsSync(".template")) {
fs.readFile(".template", function (err, data) {
if (err) {
callServerError(500, err);
return;
}
var id = uobject.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", function (err2, data2) {
if (err2) {
callServerError(500, err2);
return;
}
res.writeHead(200, "OK", headers);
res.end(
data.toString().replace("{websiteContents}", data2.toString())
);
});
} else {
callServerError(404);
}
});
} else {
callServerError(
500,
new Error("Server is misconfigured - .template file missing")
);
}
} else if (href == "/") {
redirect("/page.svr");
} else {
elseCallback();
}
```
By using `callServerError`, you can handle errors effectively and provide appropriate error responses to the client, preventing SVR.JS from crashing due to unhandled exceptions.