JS推送Discord webhook时触发userId is not defined报错

• 调用Roblox接口可正常获取对应用户名，代码能正常输出用户名内容
• 构造Discord webhook推送消息的缩略图字段、拼接userId参数时，运行抛出userId is not defined错误
• 移除缩略图配置项时代码可正常运行，需求为同时保留userId、username的正常调用，实现Roblox交易通知推送功能

原实现代码如下：

const getUsername = userId => new Promise(resolve => {
    fetch('https://users.roblox.com/v1/users/' + userId)
    .then(res => res.json())
    .then(body => resolve(body.name || 'Unknown'))
    .catch(() => resolve('Unknown'))
})
            (async () => {
                const username = await getUsername(nextInQueue.offers[0].userId);
                consola.success(`[${username}] has ok items`)
                
                fetch(config.webhook, {
                    method: 'POST',
                    headers: {
                        'content-type': 'application/json'
                    },
                    body: JSON.stringify({
                        "content": null,
                        "embeds": [
                            {
                                "title": ":tada: Trade sent to: " + username + " :tada:",
                                "color": 28420,
                                "fields": [
                                    {
                                        "name": "Cool Items:",
                                        "value": itemNameList.join('\n')
                                    },
                                    {
                                        "name": "Okay items:",
                                        "value": toreceiveList.join('\n')
                                    }
                                ],
                                "author": {
                                  "name": "Expoorttoo",
                                  "icon_url": "https://i.pinimg.com/736x/4b/69/74/4b6974aef5d96580140ef2686072af3f.jpg"
                                },
                                "footer": {
                                    "text": Sentto.toLocaleString() + " sent & " + tradeQueue.length.toLocaleString() + " set in queue"
                                },
                                "thumbnail": {
                                    "url": "https://www.roblox.com/headshot-thumbnail/image?userId=" + userId + "&width=420&height=420&format=png"
                                }
                            }
                        ]
                    })
                })
            })().catch();
        }

userId是getUsername函数的形参，作用域仅限getUsername函数内部。外层异步立即执行函数拼接缩略图URL时直接引用userId，当前作用域下没有声明该变量，直接触发未定义报错。

在异步函数作用域内先声明变量存储目标userId，再分别用于调用接口获取用户名、拼接缩略图URL即可。

修复后可运行代码：

const getUsername = userId => new Promise(resolve => {
    fetch('https://users.roblox.com/v1/users/' + userId)
    .then(res => res.json())
    .then(body => resolve(body.name || 'Unknown'))
    .catch(() => resolve('Unknown'))
})
(async () => {
    // 提前将userId存入当前作用域变量
    const targetUserId = nextInQueue.offers[0].userId;
    const username = await getUsername(targetUserId);
    consola.success(`[${username}] has ok items`)
    
    fetch(config.webhook, {
        method: 'POST',
        headers: {
            'content-type': 'application/json'
        },
        body: JSON.stringify({
            "content": null,
            "embeds": [
                {
                    "title": ":tada: Trade sent to: " + username + " :tada:",
                    "color": 28420,
                    "fields": [
                        {
                            "name": "Cool Items:",
                            "value": itemNameList.join('\n')
                        },
                        {
                            "name": "Okay items:",
                            "value": toreceiveList.join('\n')
                        }
                    ],
                    "author": {
                      "name": "Expoorttoo",
                      "icon_url": "https://i.pinimg.com/736x/4b/69/74/4b6974aef5d96580140ef2686072af3f.jpg"
                    },
                    "footer": {
                        "text": Sentto.toLocaleString() + " sent & " + tradeQueue.length.toLocaleString() + " set in queue"
                    },
                    "thumbnail": {
                        // 调用当前作用域存储的userId变量拼接地址
                        "url": `https://www.roblox.com/headshot-thumbnail/image?userId=${targetUserId}&width=420&height=420&format=png`
                    }
                }
            ]
        })
    })
// 补全catch错误回调，方便后续排查运行问题
})().catch(console.error);

内容的提问来源于stack exchange，提问作者user18383426