Fake terminal for my future text-based RPG game

terminal.js

define(function () {
    function Terminal($root, options = {}) {
        if (!document) {
            console.error("Cannot find HTML document.")
            return
        }

        this.$root = $root || document.body
        this.debug = options.debug || false
        this.nodeMap = {
            root: document.createElement('form'),
            input: document.createElement('input')
        }
        this.lastInput = null
        this.currentInput = null

        this.onChange = null

        this.listenerMap = {
            /* key: callback */
        }
    }

    Terminal.prototype.addListener = function (key, callback) {
        if (!key || !callback) {
            console.error('Invalid props for Terminal.addListener')
            return
        }

        this.listenerMap[key] = callback
    }

    Terminal.prototype.emit = function (payload) {
        if (this.onChange !== null && typeof this.onChange === 'function') {
            this.onChange(payload)
        }

        const keys = Object.keys(this.listenerMap)
        if (keys.length > 0) {
            keys.forEach(key => {
                // Dispatch the event.
                this.listenerMap[key](payload);
            });
        }
    }

    /**
     * @deps Terminal.emit
    */
    Terminal.prototype.handleInput = function (value, callback) {
        /* @TODO breakdown to a word processor module */
        if (this.lastInput !== this.currentInput) {
            this.lastInput = this.currentInput
        }

        if (this.currentInput !== value) this.currentInput = value

        // @TODO enhance word processing
        const word1 = value.split(" ")[0];
        const word2 = value.split(" ")[1];
        const word3 = value.split(" ")[2];

        // Side-effects
        this.emit([word1, word2, word3])

        callback()
    }

    // Method to execute after terminal appended to document.body
    Terminal.prototype.finalize = function () {
        if (this.nodeMap.input.isConnected) {
            this.nodeMap.input.focus();
        }
    }

    /**
     * @deps Terminal.handleInput
     * @deps Terminal.finalize
    */
    Terminal.prototype.init = function () {
        this.nodeMap.input.name = 'input'

        this.nodeMap.root.autocomplete = 'off'
        this.nodeMap.root.onsubmit = (e) => {
            e.preventDefault()

            const { value } = this.nodeMap.input

            if (this.debug) {
                const log = document.createElement('p')
                log.innerHTML = value
                this.nodeMap.root.appendChild(log)
            }

            this.handleInput(value.toLowerCase(), () => {
                this.nodeMap.input.value = "";
            });
        }

        // Assemblages
        this.nodeMap.root.appendChild(this.nodeMap.input);

        this.$root.appendChild(this.nodeMap.root);

        this.finalize()
    }

    return Terminal
})