In Express.js, you can add type to an error handler middleware function by importing the ErrorRequestHandler
type from express
package like so:
import type { ErrorRequestHandler } from 'express';
You may add the type to the error handler function in the following ways:
// ... const errorHandler: ErrorRequestHandler = (err, req, res, next) => {}; app.use(errorHandler);
// ... app.use(((err, req, res, next) => {}) as ErrorRequestHandler);
If you haven't installed the type definitions for Express.js, then make sure to add them to the dev dependencies list in your package.json
, for example, like so:
npm install --save-dev @types/express
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