Safe accessing of Map?

[potent veldt]

let map = new Map<number, number>();
map[3] = 5; //is there any way to get an error for this? maybe tooling
.set method should be used. the code is valid, but it will cause bugs difficult to find

[light tide]

let map = new Map<number, number>();
map[3] = 5;

!ts

[lapis wagon]

let map = new Map<number, number>();
map[3] = 5;
//^^^^
// Element implicitly has an 'any' type because type 'Map<number, number>' has no index signature. Did you mean to call 'map.set'?

[light tide]

It already errors.

[potent veldt]

@light tide thanks. I used swc and it seems to pass there

[light tide]

Tools like swc do not type check, they only transpile.

You still need a step with tsc to do the type checking (which is slow), while you use tools like swc to do transpiling (which is fast) for hot reload/building.

[potent veldt]

any idea how I can get it typechecked?

oh well how would I achieve that using vscode?

[light tide]

If you mean for a build step, you can just call tsc -p . --noEmit, usually I have it as a script in package.json

In VS Code you should already get the error provided by TS language server.

[potent veldt]

ok I pasted the code you evaluated in a new file x.ts
VSCode shows the syntax is recognized as typescript in the bottom right corner

it recognizes other errors, but the error you showed is not detected

[potent veldt]

so I assume the language server is working, but not conforming to your assumption

at this point I would be happy if it was just "shown in red color" in the file

[light tide]

Do you have a tsconfig.json?

[potent veldt]

no

[light tide]

Well you need one for language server to know this is a TS project.

[potent veldt]

I'll try that

I'm confused about the matter:
does tsconfig.json belong to a certain vscode extension?

just adding an empty file with that name has no effect

[light tide]

You need to put stuffs in there, an empty file won't do.

You can take a look at https://www.typescriptlang.org/docs/handbook/tsconfig-json.html and specifically you can use one of the bases in https://github.com/tsconfig/bases

[potent veldt]

ok thanks

i just figured out:

tsc --init
creates a proper file so exactly what you said happens

meaning "it puts stuff in there"
so that the discussed error finally shows

!resolved

thank you a lot!

It just required strict mode

{
  "compilerOptions": {
    "strict": true
  }
}

[light tide]

There are tons of options in tsconfig.json, if this is a learning project then do take some time and look at some of the options used by the bases and try them out.

But yeah strict is the bare minimum to make TS useful.