isError

Checks if a value is an Error object.

const result = isError(value);

Reference

isError(value)

Use isError when you want to check if a value is an Error object. It can be used as a type guard in TypeScript to narrow the value's type to Error. Particularly useful in try-catch blocks or API response processing.

import { isError } from 'es-toolkit/predicate';

// Checking Error objects
isError(new Error('Something went wrong')); // true
isError(new TypeError('Type error')); // true

// Distinguishing from other types
isError('error'); // false
isError({ name: 'Error', message: 'Custom error' }); // false

When used as a type guard in TypeScript, the value's type is narrowed.

function handleError(value: unknown) {
  if (isError(value)) {
    // value is narrowed to Error
    console.log(`Error occurred: ${value.message}`);
    return value.name;
  }
  return 'Not an error';
}

Parameters

• value (unknown): The value to check if it's an Error object.

Returns

(value is Error): Returns true if the value is an Error object, false otherwise.