express调用next();

Question

function a(){
    var a1 = 'Hello World!';
    next();
}

app.get('/b', a, function (req, res) {
  res.send(a1);
});

我应该如何获取上一个方法里的a1变量；

Answer 1

function a(req, res, next) {
    const a1 = 'this is a1'
    //req.a1 = a1
    res.locals.a1 = a1
    next()
}

app.get('/b', a, (req, res) => {
    res.send(res.locals.a1)
})

等等方法

Answer 2

function a(){
    var a1 = 'Hello World!';
    next(a1);
}

app.get('/b', a, function (a1, req, res) {
  res.send(a1);
});