Array.map（）和Array.forEach（）返回原始数组

Question

app.post('/test', (req, res) => {
    let grid = req.body.dayGrid

    grid.map(week => {
        week.map(day => {
            return day+'!'
        })
    })

    res.json(grid)
})

为什么此代码返回没有附加'！'的原始数组？

Array.forEach（）也会发生同样的情况

Answer 1

因为app.post('/test', (req, res) => { let grid = req.body.dayGrid grid = grid.map(week => week.map(day => day+'!')) res.json(grid) }) 并没有替换原始对象，而是返回了新对象。

{{1}}

Answer 2

您要从请求正文返回原始网格数组。 试试这个

app.post('/test', (req, res) => {
    let grid = req.body.dayGrid

     const result = grid.map(week => {
        return week.map(day => {
            return day+'!'
        })
    })

    res.json(result)
})