Question

所以我仍然是nodejs的初学者，当我在浏览器中运行http://127.0.0.1:3000/时，我得到此消息Cannot GET /，这是因为我使用了switch语句。我不能在app.get内使用开关吗？我想使代码DRY，这就是我使用开关的原因。

 const express = require('express');
        const app = express();
        const port = 3000;
        const hostname = 'localHost';
        app.get('/:main/:sub/:sub2', (req, res) => {
            let main = String(req.params.main).toLowerCase();
            let sub = String(req.params.sub).toLowerCase();
            let sub2 = String(req.params.sub2).toLowerCase();
            switch (main) {
                case "":
                    res.send(`Hi there welcome to my assignment`);
                case "speak":
                    {
                        switch (sub) {
                            case "pig":
                                res.send(`The pig says 'Oink'`);
                            case "cow":
                                res.send(`The cow says 'Moo'`);
                            case "dog":
                                res.send(`The dog says 'Woof Woof!'`);
                            case "*":
                                res.send(`sorry no one speaks here!`);
                        }
                    }
                case "repeat":
                    {
                        if (sub2 === !NaN) {
                            for (let i = 0; i < sub2; i++) {
                                res.send(`${sub}`);
                            }
                        }
                    }
                default:
                    res.send(`Page not found!`);
            }
        });
        app.listen(port, hostname, () => {
            console.log(`server has started`)
        });

Answer 1

您的空字符串大小写不是有效的参数，无法在main中进行搜索。

使用app.get创建默认路由：

 const express = require('express');
        const app = express();
        const port = 3000;
        const hostname = 'localHost';
        app.get("/", (req, res) => res.send("Welcome to my assignment"));
        app.get('/:main/:sub/:sub2', (req, res) => {
            let main = String(req.params.main).toLowerCase();
            let sub = String(req.params.sub).toLowerCase();
            let sub2 = String(req.params.sub2).toLowerCase();
            switch (main) {
                case "speak":
                    {
                        switch (sub) {
                            case "pig":
                                res.send(`The pig says 'Oink'`);
                                break;
                            case "cow":
                                res.send(`The cow says 'Moo'`);
                            break;
                            case "dog":
                                res.send(`The dog says 'Woof Woof!'`);
                            break;
                            case "*":
                                res.send(`sorry no one speaks here!`);
                            break;
                        }
                    }
                case "repeat":
                    {
                        if (!Number.isNaN(sub2)) {
                            let str = "";
                            for (let i = 0; i < sub2; i++) {
                                str+=sub;

                            }
                            res.send(str);
                        }
                        break;
                    }
                default:
                    res.send(`Page not found!`);
                    break;
            break;
            }
        });
        app.listen(port, hostname, () => {
            console.log(`server has started`)
        });

编辑，我还调整了“重复”功能，使其正常工作。 !NaN始终为true。您的原始代码基本上说if(sub2 === true)，但从来没有。我使用!Number.isNaN条件方法进行了修改。然后，我将一个字符串连接起来并输出n次。

在Express JS中使用get请求中的switch返回错误为什么？

1 个答案: