webpack/lib/prefetch/ChunkPrefetchStartupRuntimeModule.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";

const RuntimeGlobals = require("../RuntimeGlobals");
const RuntimeModule = require("../RuntimeModule");
const Template = require("../Template");

/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../Compilation")} Compilation */
/** @typedef {import("../RuntimeTemplate")} RuntimeTemplate */

class ChunkPrefetchStartupRuntimeModule extends RuntimeModule {
	/**
	 * @param {{ onChunks: Chunk[], chunks: Set<Chunk> }[]} startupChunks chunk ids to trigger when chunks are loaded
	 */
	constructor(startupChunks) {
		super("startup prefetch", RuntimeModule.STAGE_TRIGGER);
		this.startupChunks = startupChunks;
	}

	/**
	 * @returns {string | null} runtime code
	 */
	generate() {
		const { startupChunks } = this;
		const compilation = /** @type {Compilation} */ (this.compilation);
		const chunk = /** @type {Chunk} */ (this.chunk);
		const { runtimeTemplate } = compilation;
		return Template.asString(
			startupChunks.map(
				({ onChunks, chunks }) =>
					`${RuntimeGlobals.onChunksLoaded}(0, ${JSON.stringify(
						// This need to include itself to delay execution after this chunk has been fully loaded
						onChunks.filter(c => c === chunk).map(c => c.id)
					)}, ${runtimeTemplate.basicFunction(
						"",
						chunks.size < 3
							? Array.from(
									chunks,
									c =>
										`${RuntimeGlobals.prefetchChunk}(${JSON.stringify(c.id)});`
								)
							: `${JSON.stringify(Array.from(chunks, c => c.id))}.map(${
									RuntimeGlobals.prefetchChunk
								});`
					)}, 5);`
			)
		);
	}
}

module.exports = ChunkPrefetchStartupRuntimeModule;