webpack/lib/prefetch/ChunkPreloadTriggerRuntimeModule.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("../RuntimeTemplate")} RuntimeTemplate */

class ChunkPreloadTriggerRuntimeModule extends RuntimeModule {
	/**
	 * @param {Record<string|number, (string|number)[]>} chunkMap map from chunk to chunks
	 */
	constructor(chunkMap) {
		super(`chunk preload trigger`, RuntimeModule.STAGE_TRIGGER);
		this.chunkMap = chunkMap;
	}

	/**
	 * @returns {string} runtime code
	 */
	generate() {
		const { chunkMap } = this;
		const { runtimeTemplate } = this.compilation;
		const body = [
			"var chunks = chunkToChildrenMap[chunkId];",
			`Array.isArray(chunks) && chunks.map(${RuntimeGlobals.preloadChunk});`
		];
		return Template.asString([
			Template.asString([
				`var chunkToChildrenMap = ${JSON.stringify(chunkMap, null, "\t")};`,
				`${
					RuntimeGlobals.ensureChunkHandlers
				}.preload = ${runtimeTemplate.basicFunction("chunkId", body)};`
			])
		]);
	}
}

module.exports = ChunkPreloadTriggerRuntimeModule;