new to Typescript. I am reading some data from RabbitMQ channel and am converting it to JSON object. In this line I get the error
let communicationInformation = JSON.parse(newCommunication.content);
TS2345:Argument of type 'Buffer' is not assignable to parameter of type 'string'.
Do I need to cast the data? I am using Typescript 2.4.1
Amqplib.connect(amqpLibUrl, (err, connection) => {
if (!err) {
connection.createChannel((err, channel) => {
channel.consume('QueueName', newCommunication => {
if (newCommunication != null) {
let communicationInformation = JSON.parse(newCommunication.content);
// Code
}
})
})
}
});
I think the error is thrown on the input parameter of JSON.parse. Try to first call toString on it then pass to the function.
let communicationInformation = JSON.parse(newCommunication.content.toString());
I am not sure what is newCommunication.content. In my case it is a file and I had to specify encoding for fs.readFileSync:
const level = JSON.parse(fs.readFileSync('./path/to/file.json', 'utf-8'));
Next Error was error TS2531: Object is possibly 'null'.
You have to disable strictNullChecks in your compiler
Related
I'm pretty newbie with rxjs, can you please tell what's wrong with below?
interface IHTTP {
req: IncomingMessage;
res: ServerResponse;
handler?: Promise<any>;
}
server = http.createServer();
let request$: Observable<any>;
request$ = fromEvent(server, 'request').pipe(
map(([req, res]: [IncomingMessage, ServerResponse]): IHTTP => {
return { req, res } as IHTTP;
}
)
);
Compile error:
TS2345: Argument of type 'OperatorFunction<[IncomingMessage, ServerResponse], IHTTP>' is not assignable to parameter of type 'OperatorFunction<unknown, IHTTP>'. Type 'unknown' is not assignable to type '[IncomingMessage, ServerResponse]'.
I found the problem I had to define fromEvent's first argument as:
server as FromEventTarget<[http.IncomingMessage, http.ServerResponse]>
Otherwise Typescript thinks it's FromEventTarget<unknown>
I'm quite new to TypeScript and trying to understand what is the best way to approach such situation in my code.
I have array of objects that have a custom type in my system and I use Array.find method to get one of them. However I receive a compile error saying Type 'undefined' is not assignable to type IConfig.
Here's the code example -
const config: IConfig = CONFIGS.find(({ code }) => code === 'default');
// Type 'undefined' is not assignable to type IConfig
I tried to add undefined as possible type but then I get error on the next line which uses this object Object is possibly 'undefined', e.g. -
const config: IConfig | undefined = CONFIGS.find(({ code }) => code === 'default');
// Object is possibly 'undefined'
if (config.foo) {
return 'bar';
}
What is the best way to approach such type issues?
.find will return undefined if nothing in the array passes the callback test. If you're sure that default code exists in the array, then use the non-null assertion operator:
const config: IConfig = CONFIGS.find(({ code }) => code === 'default')!;
// ^
(If you weren't sure if it exists in the array, the warning you see is there to prompt you to explicitly test for if the item exists before trying to access a property on it, otherwise you'll sometimes get a runtime error:
const config: IConfig = CONFIGS.find(({ code }) => code === 'default');
if (!config) {
return 'No match found';
}
if (config.foo) {
return 'bar';
}
)
I am getting the following error from my code: If you could help me that would be amazing! I am using discord.js!
TypeError: Cannot read property 'name' of undefined at
files.forEach.file (/root/eternity-bot/eternity-bot/index.js:21:33) at
Array.forEach () at fs.readdir
(/root/eternity-bot/eternity-bot/index.js:18:9) at
FSReqWrap.oncomplete (fs.js:135:15)
fs.readdir("./commands/", (err, files) => {
if (err) return console.error(err);
files.forEach(file => {
if (!file.endsWith(".js")) return;
let props = require(`./commands/${file}`);
console.log(`Loading Command: ${props.help.name}.`);
bot.commands.set(props.help.name, props);
props.conf.aliases.forEach(alias => {
bot.aliases.set(alias, props.help.name);
})
});
});
TypeError: A TypeError is thrown when an operand or argument passed to a function is incompatible with the type expected by that operator or function.
The possible cause is your props is not loaded correctly and doesn't include any property help, thus accessing property name of unknown property help throws TypeError. Similar to following:
let obj = {
o1: {
a: 'abc'
}
};
obj.o1 // gives {a: 'abc'}, as o1 is property obj which is an object.
obj.o1.a // gives 'abc', as a is property of o1, which is property of obj.
obj.o2 // undefined, as there's no o2 property in obj.
obj.o2.a // TypeError as there's no o2 property of obj and thus accessing property a of undefined gives error.
What is happening is that the code is working perfectly fine, but there seems to be some problem with the exports of your javascript files in the commands folder. Most probably, the help property is not defined in your files.
Weird error with TypeScript:
As the image indicates, the error is:
TS2345: Argument of type 'ErrnoException' is not assignable to
parameter of type '(err: ErrnoException) => void'. Type
'ErrnoException' provides no match for the signature '(err:
ErrnoException): void'.
Here is the code that causes the error:
export const bump = function(cb: ErrnoException){
const {pkg, pkgPath} = syncSetup();
fs.writeFile(pkgPath, JSON.stringify(pkg, null, 2), cb);
};
Anybody know what's going on here?
You are sending a value with the type ErrnoException, while the function you are calling expects a function that takes a parameter of type *ErrnoException** and returns void.
You send:
let x = new ErrnoException;
While the function you call expects
let cb = function(e: ErrnoException) {};
You can change your function to receive the correct parameter like this.
export const bump = function(cb: (err: ErrnoException) => void){
const {pkg, pkgPath} = syncSetup();
fs.writeFile(pkgPath, JSON.stringify(pkg, null, 2), cb);
};
This is my code:
let errorBadRequest = new Error("Bad request");
res.statusCode = 400;
errorBadRequest.errors = err.details.reduce(function(prev, current) {
prev[current.path] = current.message;
return prev;
}, {});
throw errorBadRequest;
I wanted to extend error attribute in error instance, but tsc said joi-utils.ts(21,23): error TS2339: Property 'errors' does not exist on type 'Error'.
The structure of errors is {fieldname: fieldmsg}, it's according to my joi request schema to decide.
How do I solve the error from typescript compiler? I think I need to declare a interface and be designate the attribute.
Property 'errors' does not exist on type 'Error'.
Create a file called error-extension.d.ts and have the following:
interface Error {
errors: Error;
}
More : https://basarat.gitbooks.io/typescript/content/docs/types/lib.d.ts.html
I find when initialing the Error class, actually it hasn't errors in Error . It should make a interface and set errors to option.
This is my solution:
interface IJoiErrorException extends NodeJS.ErrnoException {
errors?: Object;
}
const errorBadRequest: IJoiErrorException = new Error("Bad request");