使用字符串变量访问对象。 JavaScript的

Question

这是不和谐僵尸我试图创建代码：

const Discord = require('discord.js'); 
const config = require("./config.json"); 
const bot = new Discord.Client(); 

var prefix = '!'; 
var allqueues = []; 

function queue(game,pplneeded,tag){ 
    this.game = game; 
    this.pplneeded = pplneeded; 
    this.ppljoined = 1;  
    this.tag = tag; 
    allqueues.push(tag); 
} 
bot.on('message',(message) => { 
    if(message.content.startsWith(prefix+'prefix')){ 
     var member = message.mentions.members.first(); 

     prefix=(message.content).split(" ")[1]; 
     message.channel.send('The command prefix has been set to '+(message.content).split(/\s+/g)[1] + ' .'); 
} 
if(message.content == (prefix+'rules')){ 
    message.channel.send('I\'ll keep these rules short and sweet, \'cuz this is just a casual gaming server. \n No spamming. Alright, that\'s it.'); 
} 
if(message.content == (prefix+'help')){ 
    message.channel.send('Simply type **' + prefix + 'q** ***game people_needed tag*** to create a queue, and **' + prefix + 'j** ***tag*** to join a queue.'); 
    message.channel.send('Type **' + prefix + 'eq** ***tag*** to exit a queue, and **' + prefix + 'd** ***tag*** to dismantle a queue.'); 
    message.channel.send('Type **' + prefix + 'inf** ***tag*** to find info about a queue.'); 
} 
if(message.content.startsWith(prefix+'q')){ 
    var a = message.content.split(/\s+/g); 
    a[3] = new queue(a[1],a[2],a[3]); 
    message.channel.send(a[1]+' '+a[2]+' '+a[3].tag); 
    message.channel.send('A new queue was made! Type **' + prefix + 'j ' + a[3].tag + '** to join this '+a[1]+' queue!') 
    message.channel.send(allqueues); 
} 
if(message.content.startsWith(prefix+'j')){ 
    var b = message.content.split(/\s+/g); 
    if (b[2]=undefined){ 
     message.channel.send('That\'s not a valid tag!') 
     return; 
    }else{ 
     b[2].ppljoined=b[2].ppljoined+1; 
     message.channel.send(message.author + ' has joined the ' + b[2] + 'queue!~~'); 
     if (b[2].ppljoined==b[2].pplneeded){ 
      message.channel.send(b[2] + ' has all the needed people!'); 
      index = allqueues.indexOf(b[2]) 
      allqueues.splice(index, 1); 
     } 
    } 

} 
}); 

bot.login(config.token); 

的问题是，我不知道如何访问的对象之一与“B”阵列。正如你所看到的，我尝试使用b[3]，但那是徒劳的。请帮忙。如果它可以提供一些线索，这里是错误的文字，当我键入!q game 5 tagyoureit然后!j tagyoureit在一个不和谐的服务器，其中BOT是：

C:\Users\----\Desktop\gamebot\index.js:42 
     b[2].ppljoined=b[2].ppljoined+1; 
         ^

TypeError: Cannot read property 'ppljoined' of undefined 
    at Client.bot.on (C:\Users\----\Desktop\gamebot\index.js:42:32) 
    at emitOne (events.js:115:13) 
    at Client.emit (events.js:210:7) 
    at MessageCreateHandler.handle (C:\Users\----\Desktop\gamebot\node_modules\discord.js\src\client\websocket\packets\handlers\M 
essageCre 
ate.js:9:34) 
at WebSocketPacketManager.handle (C:\Users\----\Desktop\gamebot\node_modules\discord.js\src\client\websocket\packets\WebSocketP 
acketMa 
nager.js:102:65) 
at WebSocketConnection.onPacket (C:\Users\----\Desktop\gamebot\node_modules\discord.js\src\client\websocket\WebSocketConnection.js:325 
:35) 
    at WebSocketConnection.onMessage (C:\Users\--\Desktop\gamebot\node_modules\discord.js\src\client\websocket\WebSocketConnectio 
n.js:28 
8:17) 
    at WebSocket.onMessage (C:\Users\---- 
\Desktop\gamebot\node_modules\ws\lib\EventTarget.js:103:16) 
    at emitTwo (events.js:125:13) 
    at WebSocket.emit (events.js:213:7) 

Answer 1

阵列在Javascript是零索引，这意味着数组中的第一个元素在索引0，第二个1，依此类推。既然你是b数组中寻找第二个元素，你想b[1]而不是b[2]

Answer 2

多少元素是b数组中？在分割message.content以确保后，尝试console.log(b)。

此外，如果b[2]未定义，但代码在if (b[2]=undefined){语句中（只有一个等号），代码应该放入if语句中。尝试将其更改为if (b[2] == undefined){或if (b[2]){