How to Ignore errors in TypeScript files

# Ignore errors using // @ts-ignore

Use // @ts-ignore to ignore the type checking errors on the next line in a TypeScript file.

If you use a linter, you might have to add a comment to also suppress linting errors when using ts-ignore.

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// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-ignore
function sum(a, b) {
  return a + b;
}

The // @ts-ignore comment ignores all type-checking errors for a single line.

The function's parameters are not typed, however, no error is raised because we used the comment.

# Ignore errors using // @ts-expect-error

The @ts-expect-error comment can also be used to ignore errors for a single line.

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// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-expect-error
function sum(a, b) {
  return a + b;
}

The // @ts-expect-error will ignore all type errors on the next line, but if there aren't any errors, TypeScript will inform us that using @ts-expect-error was unnecessary.

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// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-expect-error
console.log('bobbyhadz.com' / 0);

// ⛔️ Error: Unused '@ts-expect-error' directive.ts(2578)
// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-expect-error
console.log(100 * 100);

# When to use ts-ignore and ts-expect-error

That's the main difference between ts-ignore and ts-expect-error - // @ts-ignore doesn't alert us if the next line has no errors.

For example, you would use @ts-expect-error if you have a function that takes a parameter of type string, but need to test it with parameters of different types.

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function logMessage(message: string) {
  if (typeof message !== 'string') {
    return 'message has to be a string';
  }

  console.log(message);
  return message;
}

// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-expect-error
const result = logMessage(42);

if (result === 'message has to be a string') {
  console.log('test successful');
}

If we don't add the @ts-expect-error comment, we will get a type-checking error, because the function expects a string, and not a number.

This way we can still test our function, and we will get alerted if there is no need for a @ts-expect-error comment.

I've also written a detailed guide on how to disable type checking for a file or a line in TS.

# Ignore all errors in a file

Use the @ts-nocheck comment to ignore all type-checking errors in a file.

Copied!
// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-nocheck

function sum(a, b) {
  return a + b;
}

You often have to ignore type-checking errors for an entire file when your project has type-checking for JavaScript files enabled.

If you don't use a linter or don't use any rules that prevent you from using ts comments, remove the line.