NoMoreAcronyms/commands/countChars.ts

const { SlashCommandBuilder, Discord, codeBlock } = require('discord.js');

module.exports = {
	data: new SlashCommandBuilder()
		.setName('count_chars')
		.setDescription('Counts the number of characters in a string')
		.addStringOption(option =>
			option.setName('string')
				.setDescription("String to count characters in")
				.setRequired(false)
		)
		.addStringOption(option =>
			option.setName('messageid')
				.setDescription("Message ID of message to count characters in")
				.setRequired(false)
		),
	async execute(interaction, client) {
		var inputString;

		if (interaction.options.getString('string') !== null) {
			inputString = interaction.options.getString('string');
		} else if (interaction.options.getString('messageid') !== null) {
			var messageId = interaction.options.getString('messageid');
			const messagefromId = await client.channels.cache.get(interaction.channel.id).messages.fetch(messageId);
			inputString = messagefromId.content;
		}

		await interaction.reply("Input: `" + inputString + "`\n" + "Output: " + codeBlock("", countChars(inputString)));
		console.log("User " + interaction.user.tag + " ran /count_chars");
	},
};

function countChars(string) {
	var outputString = "";
	string = string.toLowerCase();
	var letterCount = Array(65535).fill(0); // Creates an array with 26 values, all equaling 0.
	for (let i = 0; i < string.length; ++i) {
		let currentChar = string.charAt(i);
		let arrayIndex = currentChar.charCodeAt(0);
		if (string.charAt(i).search(/^[A-Z]+$/) === 0) {
			arrayIndex += 32; //This should make it cast any uppercase characters to lowercase
		}
		letterCount[arrayIndex]++;
	}
	for (let i = 0; i < letterCount.length; ++i) {
		if (letterCount[i] > 0) {
			outputString += "Number of " + String.fromCharCode(i).toUpperCase() + "'s: " + letterCount[i] + "\n";
		}
	}
	return outputString;
}
//console.log(countChars("test string"));