Expressjs 多个可选参数触发请求处理程序两次

Question

Hello I need a second pair of eyes because I'm not sure why this is happening... I want to create 1 request handler which might accept 0 or 1 or 2 parameters eg: http://hocalhost:3000/{seed}/{size} , seed and size parameters must be optional.

However the below example doesn't work and the console.log is being printed twice. This doesn't happen if I change the handlers route to /api/:seed?/:size? . Why is this happening & what am I doing wrong?

const sharp = require('sharp');
const express = require('express');
const settings = require('./settings');

const app = express();

const calculateDensity = (s) => {

    return (72 * s) / 180;

}

app.get('/:seed?/:size?', (req, res) => {
        
    console.log('Why am I seeing this log?');

    res.end();

})

app.listen(settings.PORT, () => {
    console.log(`Example app listening at http://localhost:${settings.PORT}`)
})

Answer 1

So this is your default route

app.get('/:seed?/:size?', (req, res) => {
        
    console.log('Why am I seeing this log?');

    res.end();

})

Lets have another route

app.get('/test', (req, res) => {
        
    console.log('Test called');

    res.end();

})

Now on browser localhost:port/test Now which route will call. As per your code it will consider that you are calling default route, where your first two argument is optioal.

So always default route will called. and test route skipped. Because test is now parameter of default route. Not another route

Think deeply Either test route work or default route

Answer 2

Browser automatically called favicon.ico after load. it load twice for favicon.ico and the route we define.

We can resolve it like below code

app.get('/favicon.ico', (req, res) => {
    res.end()
})

app.get('/:seed?/:size', (req, res) => {
    console.log(req.url)
    if (req.url !== "/favicon.ico") {
        console.log('Why am I seeing this log?');
    }
    res.end();
})