Stuck on 'registering slash commands' on deploy-commands.js

I'm new to making Discord Bots so I can't figure out what the problem is. So basically I want to make a bot based on Discord.Js guide. I'm using V14 version. I rewrote code from guild commands section and when I insert node deploy-commands.js (in which file I inserted the code) an error occurs

PS E:\PatBot V2> node deploy-commands.js

Started refreshing 0 application (/) commands.

DiscordAPIError[50035]: Invalid Form Body

application_id[NUMBER_TYPE_COERCE]: Value "undefined" is not snowflake.

at SequentialHandler.runRequest (E:\PatBot V2\node_modules\@discordjs\rest\dist\index.js:659:15)

at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

at async SequentialHandler.queueRequest (E:\PatBot V2\node_modules\@discordjs\rest\dist\index.js:458:14)

at async REST.request (E:\PatBot V2\node_modules\@discordjs\rest\dist\index.js:902:22)

at async E:\PatBot V2\deploy-commands.js:24:16 {

requestBody: { files: undefined, json: [] },

rawError: {

code: 50035,

errors: { application_id: [Object] },

message: 'Invalid Form Body'

},

code: 50035,

status: 400,

method: 'PUT',

url: 'https://discord.com/api/v10/applications/undefined/guilds/1037350741880352869/commands'

}

​

I tried searching for tutorials on the internet but couldn't find anything based on this guide.

The whole code is based on a guide so variable names aren't changed