Error Handling By a Middleware #javascript #wecommit100xshare

What is a Middleware

A middleware in brief is simply a function that intercepts the request in order to apply certain logic before it reaches its destination: the request handler. Not only they intecept the request, but also the response. After the request handler does its job when receiving the request, the response also passes again through the same middleware that intercepted the request before reaching its destination: the client or web browser.

Error handling in Express.js happens by simply defining a middleware (function) that accepts 4 parameters: error, request, response, next as follows:

How to handling error in Javascripit

function funcLoop(x) {
    console.log(x);
    decodeURIComponent("%"); // URIError
    throw new RangeError("The argument must be between -500 and 500."); // RangeError
    throw new EvalError("Hello"); // EvalError
    // const r = x + a; // ReferenceError
}
const x = 0
try {
    funcLoop(x);
} catch (err) {
    console.log(`[funcLoop](${JSON.stringify(x)})`, JSON.stringify({
        name: err.name,
        message: err.message,
        stack: err.stack,
    }))
}        

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