shaku/src/assets/json_asset.js

A simple and effective JavaScript game development framework that knows its place!

/**
 * Implement json asset type.
 * 
 * |-- copyright and license --|
 * @module     Shaku
 * @file       shaku\src\assets\json_asset.js
 * @author     Ronen Ness (ronenness@gmail.com | http://ronenness.com)
 * @copyright  (c) 2021 Ronen Ness
 * @license    MIT
 * |-- end copyright and license --|
 * 
 */

'use strict';
const Asset = require("./asset");


/**
 * A loadable json asset.
 * This asset type loads JSON from a remote file.
 */
class JsonAsset extends Asset
{
    /** @inheritdoc */
    constructor(url)
    {
        super(url);
        this._data = null;
    }

    /**
     * Load the JSON data from the asset URL.
     * @returns {Promise} Promise to resolve when fully loaded.
     */
    load()
    {
        return new Promise((resolve, reject) => {

            var request = new XMLHttpRequest();
            request.open('GET', this.url, true);
            request.responseType = 'json';     

            // on load, validate audio content
            request.onload = () => 
            {
                if (request.readyState == 4) {
                    if (request.response) {
                        this._data = request.response;
                        this._notifyReady();
                        resolve();
                    }
                    else {
                        if (request.status === 200) {
                            reject("Response is not a valid JSON!");
                        }
                        else {
                            reject(request.statusText);
                        }
                    }
                }
            }

            // on load error, reject
            request.onerror = (e) => {
                reject(e);
            }

            // initiate request
            request.send();
        });
    }

    /**
     * Create the JSON data asset from object or string.
     * @param {Object|String} source Data to create asset from.
     * @returns {Promise} Promise to resolve when asset is ready.
     */
    create(source)
    {
        return new Promise((resolve, reject) => {

            // make sure data is a valid json + clone it
            try
            {
                if (source) {
                    if (typeof source === 'string') {
                        source = JSON.parse(source);
                    }
                    else {
                        source = JSON.parse(JSON.stringify(source));
                    }
                }
                else {
                    source = {};
                }
            }
            catch (e)
            {
                return reject("Data is not a valid JSON serializable object!");
            }

            // store data and resolve
            this._data = source;
            this._notifyReady();
            resolve();
        });
    }

    /**
     * Get json data.
     * @returns {*} Data as dictionary.
     */
    get data()
    {
        return this._data;
    }

    /** @inheritdoc */
    get valid()
    {
        return Boolean(this._data);
    }
    
    /** @inheritdoc */
    destroy()
    {
        this._data = null;
    }
}


// export the asset type.
module.exports = JsonAsset;