webpack/lib/prefetch/ChunkPreloadTriggerRuntimeModule.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("../Compilation")} Compilation */
/** @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 | null} runtime code
	 */
	generate() {
		const { chunkMap } = this;
		const compilation = /** @type {Compilation} */ (this.compilation);
		const { runtimeTemplate } = 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;