webpack/lib/serialization/PlainObjectSerializer.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

/** @typedef {import("./ObjectMiddleware").ObjectDeserializerContext} ObjectDeserializerContext */
/** @typedef {import("./ObjectMiddleware").ObjectSerializerContext} ObjectSerializerContext */

const cache = new WeakMap();

class ObjectStructure {
	constructor() {
		this.keys = undefined;
		this.children = undefined;
	}

	getKeys(keys) {
		if (this.keys === undefined) this.keys = keys;
		return this.keys;
	}

	key(key) {
		if (this.children === undefined) this.children = new Map();
		const child = this.children.get(key);
		if (child !== undefined) return child;
		const newChild = new ObjectStructure();
		this.children.set(key, newChild);
		return newChild;
	}
}

const getCachedKeys = (keys, cacheAssoc) => {
	let root = cache.get(cacheAssoc);
	if (root === undefined) {
		root = new ObjectStructure();
		cache.set(cacheAssoc, root);
	}
	let current = root;
	for (const key of keys) {
		current = current.key(key);
	}
	return current.getKeys(keys);
};

class PlainObjectSerializer {
	/**
	 * @param {object} obj plain object
	 * @param {ObjectSerializerContext} context context
	 */
	serialize(obj, context) {
		const keys = Object.keys(obj);
		if (keys.length > 128) {
			// Objects with so many keys are unlikely to share structure
			// with other objects
			context.write(keys);
			for (const key of keys) {
				context.write(obj[key]);
			}
		} else if (keys.length > 1) {
			context.write(getCachedKeys(keys, context.write));
			for (const key of keys) {
				context.write(obj[key]);
			}
		} else if (keys.length === 1) {
			const key = keys[0];
			context.write(key);
			context.write(obj[key]);
		} else {
			context.write(null);
		}
	}
	/**
	 * @param {ObjectDeserializerContext} context context
	 * @returns {object} plain object
	 */
	deserialize(context) {
		const keys = context.read();
		const obj = {};
		if (Array.isArray(keys)) {
			for (const key of keys) {
				obj[key] = context.read();
			}
		} else if (keys !== null) {
			obj[keys] = context.read();
		}
		return obj;
	}
}

module.exports = PlainObjectSerializer;