Even after ensuring the proper type checking, I am still receiving the error message "Property 'message' does not exist on type 'object'"

Question

Even after ensuring the proper type checking, I am still receiving the error message "Property 'message' does not exist on type 'object'"

I have the following code snippet:

try {
 // api call
} catch (error) {
  if (typeof error === 'object' && error !== null && 'message' in error) {
    if (typeof error.message === 'string') {
      if (error.message.match(userRejectedError)) {
        // do something
      } else {
        // do something else
      }
    }
  }
}

However, I am encountering the error:

Property 'message' does not exist on type 'object'

. Why is this happening when I have made sure to check all necessary types?

Edit: TSConfig

{
  "compilerOptions": {
    "baseUrl": ".",
    "target": "es6",
    "lib": ["dom", "dom.iterable", "esnext"],
    },
    "allowJs": true,
    "skipLibCheck": true,
    "strict": true,
    "strictNullChecks": false,
    "noImplicitAny": false,
    "forceConsistentCasingInFileNames": true,
    "noEmit": true,
    "esModuleInterop": true,
    "module": "esnext",
    "moduleResolution": "node",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "jsx": "preserve"
  },
  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx"],
  "exclude": ["node_modules"]
}

typescript

Answer 1

Answer №1

You're Not Ensuring Strict Type Checking

Currently, you are only verifying that the error instance is an object, not null, has a message property, and that the type of error.message is a string, instead of simply checking if the error instance is of type Error.

Utilize the instanceof keyword for type checking, rather than comparing with a string using typeof.

If you can guarantee that the error instance is of type Error, TypeScript can accurately infer that the instance will have the message property.

For example:

try{
/* some error-throwable code... */
} catch(error) {
  /* Use instanceof to compare types */
  if (error instanceof Error) {
    // Do something
  }
  /* Alternatively, you can use a switch statement */
  switch (error.constructor) {
    case Error:
      // Do something
  }
}

Refer to the link below for documentation on the Error type.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error

Answer 2

You're Not Ensuring Strict Type Checking

Currently, you are only verifying that the error instance is an object, not null, has a message property, and that the type of error.message is a string, instead of simply checking if the error instance is of type Error.

Utilize the instanceof keyword for type checking, rather than comparing with a string using typeof.

If you can guarantee that the error instance is of type Error, TypeScript can accurately infer that the instance will have the message property.

For example:

try{
/* some error-throwable code... */
} catch(error) {
  /* Use instanceof to compare types */
  if (error instanceof Error) {
    // Do something
  }
  /* Alternatively, you can use a switch statement */
  switch (error.constructor) {
    case Error:
      // Do something
  }
}

Refer to the link below for documentation on the Error type.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error

Even after ensuring the proper type checking, I am still receiving the error message "Property 'message' does not exist on type 'object'"

Answer №1

You're Not Ensuring Strict Type Checking

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