node.js/discord.js：类型错误：无法读取 null 的属性“setPresence”

Question

Trying a simple test, but I'm getting an error from this line: client.user.setPresence('game', { type: 'PLAYING' });

VSCode's logs:

C:\Users\dvmvged\Documents\mao>node . whoa.js
C:\Users\dvmvged\Documents\mao\whoa.js:9
client.user.setPresence('game', { type: 'PLAYING' });
            ^

TypeError: Cannot read property 'setPresence' of null
    at Object.<anonymous> (C:\Users\dvmvged\Documents\mao\whoa.js:9:13)
←[90m    at Module._compile (internal/modules/cjs/loader.js:956:30)←[39m
←[90m    at Object.Module._extensions..js (internal/modules/cjs/loader.js:973:10)←[39m
←[90m    at Module.load (internal/modules/cjs/loader.js:812:32)←[39m
←[90m    at Function.Module._load (internal/modules/cjs/loader.js:724:14)←[39m
←[90m    at Function.Module.runMain (internal/modules/cjs/loader.js:1025:10)←[39m
←[90m    at internal/main/run_main_module.js:17:11←[39m

whoa.js

    const Discord = require('discord.js');
    const client = new Discord.Client();

    client.on('ready', () => {
        console.log("Logged in.");
        client.login("token");
    });

    client.user.setPresence('test', { type: 'PLAYING' });

package.json:

{ 
    "name":"test-bot",
    "version":"1.0.0",
    "description":"simple test",
    "main":"whoa.js",
    "dependencies":{ 
        "discord.js":"^11.5.1"
    },
    "devDependencies":{ 

    },
    "scripts":{ 
        "test":"echo \"Error: no test specified\" && exit 1"
    },
    "author":"no one",
    "license":"ISC"
}

NPM version: 6.11.3

Node.js version: 12.12.0

Discord.js version: 11.5.1

EDIT: Just to let you know, I tried.setActivity and.setGame. same error.

Answer 1

I think what's happening here is a consequence of the Node.js event loop. You call an asynchronous function, .login() , and immediately attempt client.user.setPresence() before the response from .login() arrives.

Try

  .login("token")
  .then(client.user.setPresence("game", { type: "PLAYING" }));

See Node Event Loop

Answer 2

.user has not yet been populated when you called him. I'm gonna annotate the order at which things happen here.

const Discord = require('discord.js');
const client = new Discord.Client();

// #1
client.on('ready', () => {
    // #3
    console.log("Logged in.");
    client.login("token");
});

// #2
client.user.setPresence('test', { type: 'PLAYING' });

You only have a guarrantee of.user existing after the client is ready.

Whenever you use a callback in node (not just in node,). you pass a function as an argument to something.

That callback may be scheduling that function to run on a later time. On this specific case case, it schelules the function which has console.log to run on a future event of the client "being ready".