webpack/lib/prefetch/ChunkPrefetchStartupRuntimeModule.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support 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("../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} runtime code
	 */
	generate() {
		const { startupChunks, chunk } = this;
		const { runtimeTemplate } = this.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;