我正在制作一个 minecraft ping discord bot，当我的服务器离线时它会抛出这个错误

Question

(node:7548) UnhandledPromiseRejectionWarning: TypeError: 无法读取 null 的属性“substr” 在客户端。 (C:\Users\RCIIND_4\Desktop\Vs Code\index.js:67:83) 在 processTicksAndRejections (internal/process/task_queues.js:95:5) （使用 node --trace-warnings ... 显示警告的创建位置） （节点：7548）UnhandledPromiseRejectionWarning：未处理的承诺拒绝。这个错误要么是因为在没有 catch 块的情况下抛出了异步函数，要么是因为拒绝了一个没有用 .catch() 处理过的承诺。要在未处理的承诺拒绝时终止节点进程，请使用 CLI 标志 --unhandled-rejections=strict（请参阅 https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode）。 （拒绝编号：1） （节点：7548）[DEP0018] 弃用警告：不推荐使用未处理的承诺拒绝。将来，未处理的承诺拒绝将以非零退出代码终止 Node.js 进程。

这是代码

const ms = require('ms')
const fetch = require('node-fetch')
const Discord = require('discord.js')
const client = new Discord.Client()

const config = require('./config.json')

/**
 * This function is used to update statistics channel
 */
const updateChannel = async () => {

    // Fetch statistics from mcapi.us
    const res = await fetch(`https://mcapi.us/server/status?ip=${config.ipAddress}${config.port ? `&port=${config.port}` : ''}`)
    if (!res) {
        const statusChannelName = `【?】Status: Offline`
        client.channels.cache.get(config.statusChannel).setName(statusChannelName)
        return false
    }
    // Parse the mcapi.us response
    const body = await res.json()

    // Get the current player count, or set it to 0
    const players = body.players.now

    // Get the server status
    const status = (body.online ? "Online" : "Offline")

    // Generate channel names
    const playersChannelName = `【?】Players: ${players}`
    const statusChannelName = `【?】Status: ${status}`

    // Update channel names
    client.channels.cache.get(config.playersChannel).setName(playersChannelName)
    client.channels.cache.get(config.statusChannel).setName(statusChannelName)

    return true
}

client.on('ready', () => {
    console.log(`Ready. Logged as ${client.user.tag}.`)
    setInterval(() => {
        updateChannel()
    }, ms(config.updateInterval))
})

client.on('message', async (message) => {

    if(message.content === `${config.prefix}force-update`){
        if (!message.member.hasPermission('MANAGE_MESSAGES')) {
            return message.channel.send('Only server moderators can run this command!')
        }
        const sentMessage = await message.channel.send("Updating the channels, please wait...")
        await updateChannel()
        sentMessage.edit("Channels were updated successfully!")
    }

    if(message.content === `${config.prefix}stats`){
        const sentMessage = await message.channel.send("Fetching statistics, please wait...")

        // Fetch statistics from mcapi.us
        const res = await fetch(`https://mcapi.us/server/status?ip=${config.ipAddress}${config.port ? `&port=${config.port}` : ''}`)
        if (!res) return message.channel.send(`Looks like your server is not reachable... Please verify it's online and it isn't blocking access!`)
        // Parse the mcapi.us response
        const body = await res.json()

        const attachment = new Discord.MessageAttachment(Buffer.from(body.favicon.substr('data:image/png;base64'.length), 'base64'), "icon.png")
        const embed = new Discord.MessageEmbed()
            .setAuthor(config.ipAddress)
            .attachFiles(attachment)
            .setThumbnail("attachment://icon.png")
            .addField("Version", body.server.name)
            .addField("Connected", `${body.players.now} players`)
            .addField("Maximum", `${body.players.max} players`)
            .addField("Status", (body.online ? "Online" : "Offline"))
            .setColor("#FF0000")
            .setFooter("Open Source Minecraft Discord Bot")
        
        sentMessage.edit(`:chart_with_upwards_trend: Here are the stats for **${config.ipAddress}**:`, { embed })
    }

})
client.login(config.token)

这是更新后的代码

const ms = require('ms')
const fetch = require('node-fetch')
const Discord = require('discord.js')
const client = new Discord.Client()

const config = require('./config.json')

/**
 * This function is used to update statistics channel
 */
const updateChannel = async () => {

    // Fetch statistics from mcapi.us
    const res = await fetch(`https://mcapi.us/server/status?ip=${config.ipAddress}${config.port ? `&port=${config.port}` : ''}`)
    if (!res) {
        const statusChannelName = `【?】Status: Offline`
        client.channels.cache.get(config.statusChannel).setName(statusChannelName)
        return false
    }
    // Parse the mcapi.us response
    const body = await res.json()

    // Get the current player count, or set it to 0
    const players = body.players.now

    // Get the server status
    const status = (body.online ? "Online" : "Offline")

    // Generate channel names
    const playersChannelName = `【?】Players: ${players}`
    const statusChannelName = `【?】Status: ${status}`

    // Update channel names
    client.channels.cache.get(config.playersChannel).setName(playersChannelName)
    client.channels.cache.get(config.statusChannel).setName(statusChannelName)

    return true
}

client.on('ready', () => {
    console.log(`Ready. Logged as ${client.user.tag}.`)
    setInterval(() => {
        updateChannel()
    }, ms(config.updateInterval))
})

client.on('message', async (message) => {

    if(message.content === `${config.prefix}force-update`){
        if (!message.member.hasPermission('MANAGE_MESSAGES')) {
            return message.channel.send('Only server moderators can run this command!')
        }
        const sentMessage = await message.channel.send("Updating the channels, please wait...")
        await updateChannel()
        sentMessage.edit("Channels were updated successfully!")
    }

    if(message.content === `${config.prefix}stats`){
        const sentMessage = await message.channel.send("Fetching statistics, please wait...")

        // Fetch statistics from mcapi.us
        const res = await fetch(`https://mcapi.us/server/status?ip=${config.ipAddress}${config.port ? `&port=${config.port}` : ''}`)
        if (!res) return message.channel.send(`Looks like your server is not reachable... Please verify it's online and it isn't blocking access!`)
        // Parse the mcapi.us response
        const body = await res.json()

        let embed = new Discord.MessageEmbed()
        .setAuthor(config.ipAddress);

if (attachment) { new Discord.MessageAttachment(Buffer.from(body.favicon.substr('data:image/png;base64,'.length), 'base64'), "icon.png")
  embed = embed.attachFiles(attachment);
}

embed = embed.setThumbnail("attachment://icon.png")
        .addField("Version", body.server.name)
        .addField("Connected", `${body.players.now} players`)
        .addField("Maximum", `${body.players.max} players`)
        .addField("Status", (body.online ? "Online" : "Offline"))
        .setColor("#FF0000")
        .setFooter("Open Source Minecraft Discord Bot");
        
        sentMessage.edit(`:chart_with_upwards_trend: Here are the stats for **${config.ipAddress}**:`, { embed })
    }

})
client.login(config.token)

Answer 1

body.favicon 是 null，但您尝试在此处使用它：

body.favicon.substr(...)

如果这个值有可能是 null（而且显然是），那么你不能假设它会有一个值。你必须先检查。从那里，您需要决定当此值为 null 时您希望代码做什么。例如，您可以像这样添加 null 检查：

const attachment = body.favicon ? new Discord.MessageAttachment(Buffer.from(body.favicon.substr('data:image/png;base64'.length), 'base64'), "icon.png") : null;

这使用 ?: 条件运算符来检查 body.favicon 是否有值。如果是，请按照当前代码进行操作。如果它没有值，请将 attachment 设置为 null。

从那里您需要决定当 attachment 为 null 时要做什么。您可能无法像那样在 Discord API 中使用它。因此，您也可以在此处在条件检查中包装一些逻辑：

let embed = new Discord.MessageEmbed()
        .setAuthor(config.ipAddress);

if (attachment) { // <--- here
  embed = embed.attachFiles(attachment)
        .setThumbnail("attachment://icon.png");
}

embed = embed.addField("Version", body.server.name)
        .addField("Connected", `${body.players.now} players`)
        .addField("Maximum", `${body.players.max} players`)
        .addField("Status", (body.online ? "Online" : "Offline"))
        .setColor("#FF0000")
        .setFooter("Open Source Minecraft Discord Bot");

---

更新

在您更新的代码中，您已经完全删除了 attachment 的定义。那肯定会简化问题。如果这是您想要做的，那么您还需要删除任何使用 attachment 的代码。例如：

let embed = new Discord.MessageEmbed()
    .setAuthor(config.ipAddress);
    .addField("Version", body.server.name)
    .addField("Connected", `${body.players.now} players`)
    .addField("Maximum", `${body.players.max} players`)
    .addField("Status", (body.online ? "Online" : "Offline"))
    .setColor("#FF0000")
    .setFooter("Open Source Minecraft Discord Bot");