Why am I unable to access function properties?

user_5512705 0
Viewed 97

I'm writing a function with refernece to callback functions. However I cannot seem to access its properties.

const example = (
   callback: (...args: unknown[]) => unknown
): void => ({
   name: callback.name // <- errors
   // ...
})

My issue is, typescript doesn't like me accessing the funciton properties.

name: callback.name 
// ts(2339): Property 'name' does not exist on type '(...args: any[]) => any'

What would be the correct way of accessing the function name (or other Function properties for that matter)?

Typescript version: "ˆ3.9.7" (latest as to the day of this post)

typescript reactjs javascript
2 Answers

Allright I found what caused it and how to fix it. This issue occured because of how my tsconfig.json was set up inside my project.

// tsconfig.json
{
  "compilerOptions": {
    "target": "es5",
    // ....
  },
}

Reason being interface Functon has only been declared in lib.es6.d.ts

So depending on the needs, in order to solve this, you can

  • Either upgrade the target version in tsconfig.json

    {
  "compilerOptions": {
     "target": "es6" // was "es5"
     // ...
  }
}

  • Or specify the "lib" to be included in compilation

    {
  "compilerOptions": {
      "target": "es5",
      "lib": ["es6", "dom", "es2016", "es2017", "es5"], // needs at least es6
     // ...
  }
}
user_55127050 
import { Dispatch, SetStateAction } from 'react'
import { FieldType, ErrorType } from 'types/FieldTypes'

const handleErrors = (
  setField: Dispatch<SetStateAction<FieldType>>,
  callback: {
    name: 'name of callback',
    run: (args) => {
      try {
        callback.run();
      } catch (e) {
      const newError: ErrorType = {
        name: callback.name,
        message: e.message,
      };
      setField((prevData) => ({
        ...prevData,
        errors: [...prevData.errors || [], newError],
      });
    }
  }
);
user_60725700
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