今回は、webpackでCSSを読み込みます。


まず、CSSのサンプルを用意しておきます。


h1 {
color: #5FC4B6;
}


次に、CSSの読み込みに必要なローダーをインストールします。


npm install -D webpack style-loader css-loader


インストールが完了したら、「webpack.config.js」と「main.js」を書き換えます。

webpack.config.js


module.exports = {
entry: './_src/main.js',
output: {
path: __dirname + '/build',
filename: 'app.js'
},
module : {
rules : [
{
test: /\.css/,
loaders: ['style-loader', 'css-loader']
}
]
}
};


main.js


import {sample01} from "./js/sample01.js";
import {sample02} from "./js/sample02.js";

import "./css/stylesheet.css";

sample01();
sample02();


ファイルの準備ができたらビルドします。


npm run build


ビルドが成功すると、buildディレクトリに全てのJSとCSSが統合されたapp.jsが作成されます。

app.js


/******/ (function(modules) { // webpackBootstrap
/******/ // The module cache
/******/ var installedModules = {};
/******/
/******/ // The require function
/******/ function __webpack_require__(moduleId) {
/******/
/******/ // Check if module is in cache
/******/ if(installedModules[moduleId]) {
/******/ return installedModules[moduleId].exports;
/******/ }
/******/ // Create a new module (and put it into the cache)
/******/ var module = installedModules[moduleId] = {
/******/ i: moduleId,
/******/ l: false,
/******/ exports: {}
/******/ };
/******/
/******/ // Execute the module function
/******/ modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
/******/
/******/ // Flag the module as loaded
/******/ module.l = true;
/******/
/******/ // Return the exports of the module
/******/ return module.exports;
/******/ }
/******/
/******/
/******/ // expose the modules object (__webpack_modules__)
/******/ __webpack_require__.m = modules;
/******/
/******/ // expose the module cache
/******/ __webpack_require__.c = installedModules;
/******/
/******/ // define getter function for harmony exports
/******/ __webpack_require__.d = function(exports, name, getter) {
/******/ if(!__webpack_require__.o(exports, name)) {
/******/ Object.defineProperty(exports, name, {
/******/ configurable: false,
/******/ enumerable: true,
/******/ get: getter
/******/ });
/******/ }
/******/ };
/******/
/******/ // getDefaultExport function for compatibility with non-harmony modules
/******/ __webpack_require__.n = function(module) {
/******/ var getter = module && module.__esModule ?
/******/ function getDefault() { return module['default']; } :
/******/ function getModuleExports() { return module; };
/******/ __webpack_require__.d(getter, 'a', getter);
/******/ return getter;
/******/ };
/******/
/******/ // Object.prototype.hasOwnProperty.call
/******/ __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
/******/
/******/ // __webpack_public_path__
/******/ __webpack_require__.p = "";
/******/
/******/ // Load entry module and return exports
/******/ return __webpack_require__(__webpack_require__.s = 0);
/******/ })
/************************************************************************/
/******/ ([
/* 0 */
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
Object.defineProperty(__webpack_exports__, "__esModule", { value: true });
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_0__js_sample01_js__ = __webpack_require__(1);
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_1__js_sample02_js__ = __webpack_require__(2);
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_2__css_stylesheet_css__ = __webpack_require__(3);
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_2__css_stylesheet_css___default = __webpack_require__.n(__WEBPACK_IMPORTED_MODULE_2__css_stylesheet_css__);

Object(__WEBPACK_IMPORTED_MODULE_0__js_sample01_js__["a" /* sample01 */])();
Object(__WEBPACK_IMPORTED_MODULE_1__js_sample02_js__["a" /* sample02 */])();

/***/ }),
/* 1 */
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
/* harmony export (immutable) */ __webpack_exports__["a"] = sample01;
function sample01() {
alert('sample01を実行!!');
}

/***/ }),
/* 2 */
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
/* harmony export (immutable) */ __webpack_exports__["a"] = sample02;
function sample02() {
alert('sample02を実行!!');
}

/***/ }),
/* 3 */
/***/ (function(module, exports, __webpack_require__) {

// style-loader: Adds some css to the DOM by adding a <style> tag

// load the styles
var content = __webpack_require__(4);
if(typeof content === 'string') content = [[module.i, content, '']];
// Prepare cssTransformation
var transform;

var options = {}
options.transform = transform
// add the styles to the DOM
var update = __webpack_require__(6)(content, options);
if(content.locals) module.exports = content.locals;
// Hot Module Replacement
if(false) {
// When the styles change, update the <style> tags
if(!content.locals) {
module.hot.accept("!!../../node_modules/css-loader/index.js!./stylesheet.css", function() {
var newContent = require("!!../../node_modules/css-loader/index.js!./stylesheet.css");
if(typeof newContent === 'string') newContent = [[module.id, newContent, '']];
update(newContent);
});
}
// When the module is disposed, remove the <style> tags
module.hot.dispose(function() { update(); });
}

/***/ }),
/* 4 */
/***/ (function(module, exports, __webpack_require__) {

exports = module.exports = __webpack_require__(5)(undefined);
// imports

// module
exports.push([module.i, "h1 {\n color: #5FC4B6;\n}\n", ""]);

// exports

/***/ }),
/* 5 */
/***/ (function(module, exports) {

/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
// css base code, injected by the css-loader
module.exports = function(useSourceMap) {
var list = [];

// return the list of modules as css string
list.toString = function toString() {
return this.map(function (item) {
var content = cssWithMappingToString(item, useSourceMap);
if(item[2]) {
return "@media " + item[2] + "{" + content + "}";
} else {
return content;
}
}).join("");
};

// import a list of modules into the list
list.i = function(modules, mediaQuery) {
if(typeof modules === "string")
modules = [[null, modules, ""]];
var alreadyImportedModules = {};
for(var i = 0; i < this.length; i++) {
var id = this[i][0];
if(typeof id === "number")
alreadyImportedModules[id] = true;
}
for(i = 0; i < modules.length; i++) {
var item = modules[i];
// skip already imported module
// this implementation is not 100% perfect for weird media query combinations
// when a module is imported multiple times with different media queries.
// I hope this will never occur (Hey this way we have smaller bundles)
if(typeof item[0] !== "number" || !alreadyImportedModules[item[0]]) {
if(mediaQuery &amp;&amp; !item[2]) {
item[2] = mediaQuery;
} else if(mediaQuery) {
item[2] = "(" + item[2] + ") and (" + mediaQuery + ")";
}
list.push(item);
}
}
};
return list;
};

function cssWithMappingToString(item, useSourceMap) {
var content = item[1] || '';
var cssMapping = item[3];
if (!cssMapping) {
return content;
}

if (useSourceMap &amp;&amp; typeof btoa === 'function') {
var sourceMapping = toComment(cssMapping);
var sourceURLs = cssMapping.sources.map(function (source) {
return '/*# sourceURL=' + cssMapping.sourceRoot + source + ' */'
});

return [content].concat(sourceURLs).concat([sourceMapping]).join('\n');
}

return [content].join('\n');
}

// Adapted from convert-source-map (MIT)
function toComment(sourceMap) {
// eslint-disable-next-line no-undef
var base64 = btoa(unescape(encodeURIComponent(JSON.stringify(sourceMap))));
var data = 'sourceMappingURL=data:application/json;charset=utf-8;base64,' + base64;

return '/*# ' + data + ' */';
}

/***/ }),
/* 6 */
/***/ (function(module, exports, __webpack_require__) {

/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/

var stylesInDom = {};

var memoize = function (fn) {
var memo;

return function () {
if (typeof memo === "undefined") memo = fn.apply(this, arguments);
return memo;
};
};

var isOldIE = memoize(function () {
// Test for IE <= 9 as proposed by Browserhacks
// @see http://browserhacks.com/#hack-e71d8692f65334173fee715c222cb805
// Tests for existence of standard globals is to allow style-loader
// to operate correctly into non-standard environments
// @see https://github.com/webpack-contrib/style-loader/issues/177
return window &amp;&amp; document &amp;&amp; document.all &amp;&amp; !window.atob;
});

var getElement = (function (fn) {
var memo = {};

return function(selector) {
if (typeof memo[selector] === "undefined") {
memo[selector] = fn.call(this, selector);
}

return memo[selector]
};
})(function (target) {
return document.querySelector(target)
});

var singleton = null;
var singletonCounter = 0;
var stylesInsertedAtTop = [];

var fixUrls = __webpack_require__(7);

module.exports = function(list, options) {
if (typeof DEBUG !== "undefined" &amp;&amp; DEBUG) {
if (typeof document !== "object") throw new Error("The style-loader cannot be used in a non-browser environment");
}

options = options || {};

options.attrs = typeof options.attrs === "object" ? options.attrs : {};

// Force single-tag solution on IE6-9, which has a hard limit on the # of <style>
// tags it will allow on a page
if (!options.singleton) options.singleton = isOldIE();

// By default, add <style> tags to the <head> element
if (!options.insertInto) options.insertInto = "head";

// By default, add <style> tags to the bottom of the target
if (!options.insertAt) options.insertAt = "bottom";

var styles = listToStyles(list, options);

addStylesToDom(styles, options);

return function update (newList) {
var mayRemove = [];

for (var i = 0; i < styles.length; i++) {
var item = styles[i];
var domStyle = stylesInDom[item.id];

domStyle.refs--;
mayRemove.push(domStyle);
}

if(newList) {
var newStyles = listToStyles(newList, options);
addStylesToDom(newStyles, options);
}

for (var i = 0; i < mayRemove.length; i++) {
var domStyle = mayRemove[i];

if(domStyle.refs === 0) {
for (var j = 0; j < domStyle.parts.length; j++) domStyle.parts[j]();

delete stylesInDom[domStyle.id];
}
}
};
};

function addStylesToDom (styles, options) {
for (var i = 0; i < styles.length; i++) {
var item = styles[i];
var domStyle = stylesInDom[item.id];

if(domStyle) {
domStyle.refs++;

for(var j = 0; j < domStyle.parts.length; j++) {
domStyle.parts[j](item.parts[j]);
}

for(; j < item.parts.length; j++) {
domStyle.parts.push(addStyle(item.parts[j], options));
}
} else {
var parts = [];

for(var j = 0; j < item.parts.length; j++) {
parts.push(addStyle(item.parts[j], options));
}

stylesInDom[item.id] = {id: item.id, refs: 1, parts: parts};
}
}
}

function listToStyles (list, options) {
var styles = [];
var newStyles = {};

for (var i = 0; i < list.length; i++) {
var item = list[i];
var id = options.base ? item[0] + options.base : item[0];
var css = item[1];
var media = item[2];
var sourceMap = item[3];
var part = {css: css, media: media, sourceMap: sourceMap};

if(!newStyles[id]) styles.push(newStyles[id] = {id: id, parts: [part]});
else newStyles[id].parts.push(part);
}

return styles;
}

function insertStyleElement (options, style) {
var target = getElement(options.insertInto)

if (!target) {
throw new Error("Couldn't find a style target. This probably means that the value for the 'insertInto' parameter is invalid.");
}

var lastStyleElementInsertedAtTop = stylesInsertedAtTop[stylesInsertedAtTop.length - 1];

if (options.insertAt === "top") {
if (!lastStyleElementInsertedAtTop) {
target.insertBefore(style, target.firstChild);
} else if (lastStyleElementInsertedAtTop.nextSibling) {
target.insertBefore(style, lastStyleElementInsertedAtTop.nextSibling);
} else {
target.appendChild(style);
}
stylesInsertedAtTop.push(style);
} else if (options.insertAt === "bottom") {
target.appendChild(style);
} else {
throw new Error("Invalid value for parameter 'insertAt'. Must be 'top' or 'bottom'.");
}
}

function removeStyleElement (style) {
if (style.parentNode === null) return false;
style.parentNode.removeChild(style);

var idx = stylesInsertedAtTop.indexOf(style);
if(idx >= 0) {
stylesInsertedAtTop.splice(idx, 1);
}
}

function createStyleElement (options) {
var style = document.createElement("style");

options.attrs.type = "text/css";

addAttrs(style, options.attrs);
insertStyleElement(options, style);

return style;
}

function createLinkElement (options) {
var link = document.createElement("link");

options.attrs.type = "text/css";
options.attrs.rel = "stylesheet";

addAttrs(link, options.attrs);
insertStyleElement(options, link);

return link;
}

function addAttrs (el, attrs) {
Object.keys(attrs).forEach(function (key) {
el.setAttribute(key, attrs[key]);
});
}

function addStyle (obj, options) {
var style, update, remove, result;

// If a transform function was defined, run it on the css
if (options.transform &amp;&amp; obj.css) {
result = options.transform(obj.css);

if (result) {
// If transform returns a value, use that instead of the original css.
// This allows running runtime transformations on the css.
obj.css = result;
} else {
// If the transform function returns a falsy value, don't add this css.
// This allows conditional loading of css
return function() {
// noop
};
}
}

if (options.singleton) {
var styleIndex = singletonCounter++;

style = singleton || (singleton = createStyleElement(options));

update = applyToSingletonTag.bind(null, style, styleIndex, false);
remove = applyToSingletonTag.bind(null, style, styleIndex, true);

} else if (
obj.sourceMap &amp;&amp;
typeof URL === "function" &amp;&amp;
typeof URL.createObjectURL === "function" &amp;&amp;
typeof URL.revokeObjectURL === "function" &amp;&amp;
typeof Blob === "function" &amp;&amp;
typeof btoa === "function"
) {
style = createLinkElement(options);
update = updateLink.bind(null, style, options);
remove = function () {
removeStyleElement(style);

if(style.href) URL.revokeObjectURL(style.href);
};
} else {
style = createStyleElement(options);
update = applyToTag.bind(null, style);
remove = function () {
removeStyleElement(style);
};
}

update(obj);

return function updateStyle (newObj) {
if (newObj) {
if (
newObj.css === obj.css &amp;&amp;
newObj.media === obj.media &amp;&amp;
newObj.sourceMap === obj.sourceMap
) {
return;
}

update(obj = newObj);
} else {
remove();
}
};
}

var replaceText = (function () {
var textStore = [];

return function (index, replacement) {
textStore[index] = replacement;

return textStore.filter(Boolean).join('\n');
};
})();

function applyToSingletonTag (style, index, remove, obj) {
var css = remove ? "" : obj.css;

if (style.styleSheet) {
style.styleSheet.cssText = replaceText(index, css);
} else {
var cssNode = document.createTextNode(css);
var childNodes = style.childNodes;

if (childNodes[index]) style.removeChild(childNodes[index]);

if (childNodes.length) {
style.insertBefore(cssNode, childNodes[index]);
} else {
style.appendChild(cssNode);
}
}
}

function applyToTag (style, obj) {
var css = obj.css;
var media = obj.media;

if(media) {
style.setAttribute("media", media)
}

if(style.styleSheet) {
style.styleSheet.cssText = css;
} else {
while(style.firstChild) {
style.removeChild(style.firstChild);
}

style.appendChild(document.createTextNode(css));
}
}

function updateLink (link, options, obj) {
var css = obj.css;
var sourceMap = obj.sourceMap;

/*
If convertToAbsoluteUrls isn't defined, but sourcemaps are enabled
and there is no publicPath defined then lets turn convertToAbsoluteUrls
on by default. Otherwise default to the convertToAbsoluteUrls option
directly
*/
var autoFixUrls = options.convertToAbsoluteUrls === undefined &amp;&amp; sourceMap;

if (options.convertToAbsoluteUrls || autoFixUrls) {
css = fixUrls(css);
}

if (sourceMap) {
// http://stackoverflow.com/a/26603875
css += "\n/*# sourceMappingURL=data:application/json;base64," + btoa(unescape(encodeURIComponent(JSON.stringify(sourceMap)))) + " */";
}

var blob = new Blob([css][/css], { type: "text/css" });

var oldSrc = link.href;

link.href = URL.createObjectURL(blob);

if(oldSrc) URL.revokeObjectURL(oldSrc);
}

/***/ }),
/* 7 */
/***/ (function(module, exports) {

/**
* When source maps are enabled, `style-loader` uses a link element with a data-uri to
* embed the css on the page. This breaks all relative urls because now they are relative to a
* bundle instead of the current page.
*
* One solution is to only use full urls, but that may be impossible.
*
* Instead, this function "fixes" the relative urls to be absolute according to the current page location.
*
* A rudimentary test suite is located at `test/fixUrls.js` and can be run via the `npm test` command.
*
*/

module.exports = function (css) {
// get current location
var location = typeof window !== "undefined" &amp;&amp; window.location;

if (!location) {
throw new Error("fixUrls requires window.location");
}

// blank or null?
if (!css || typeof css !== "string") {
return css;
}

var baseUrl = location.protocol + "//" + location.host;
var currentDir = baseUrl + location.pathname.replace(/\/[^\/]*$/, "/");

// convert each url(...)
/*
This regular expression is just a way to recursively match brackets within
a string.

/url\s*\( = Match on the word "url" with any whitespace after it and then a parens
( = Start a capturing group
(?: = Start a non-capturing group
[^)(] = Match anything that isn't a parentheses
| = OR
\( = Match a start parentheses
(?: = Start another non-capturing groups
[^)(]+ = Match anything that isn't a parentheses
| = OR
\( = Match a start parentheses
[^)(]* = Match anything that isn't a parentheses
\) = Match a end parentheses
) = End Group
*\) = Match anything and then a close parens
) = Close non-capturing group
* = Match anything
) = Close capturing group
\) = Match a close parens

/gi = Get all matches, not the first. Be case insensitive.
*/
var fixedCss = css.replace(/url\s*\(((?:[^)(]|\((?:[^)(]+|\([^)(]*\))*\))*)\)/gi, function(fullMatch, origUrl) {
// strip quotes (if they exist)
var unquotedOrigUrl = origUrl
.trim()
.replace(/^"(.*)"$/, function(o, $1){ return $1; })
.replace(/^'(.*)'$/, function(o, $1){ return $1; });

// already a full url? no change
if (/^(#|data:|http:\/\/|https:\/\/|file:\/\/\/)/i.test(unquotedOrigUrl)) {
return fullMatch;
}

// convert the url to a full url
var newUrl;

if (unquotedOrigUrl.indexOf("//") === 0) {
//TODO: should we add protocol?
newUrl = unquotedOrigUrl;
} else if (unquotedOrigUrl.indexOf("/") === 0) {
// path should be relative to the base url
newUrl = baseUrl + unquotedOrigUrl; // already starts with '/'
} else {
// path should be relative to current directory
newUrl = currentDir + unquotedOrigUrl.replace(/^\.\//, ""); // Strip leading './'
}

// send back the fixed url(...)
return "url(" + JSON.stringify(newUrl) + ")";
});

// send back the fixed css
return fixedCss;
};

/***/ })
/******/ ])


app.jsを読み込むindex.htmlを作成して実行してみます。stylesheet.cssの内容が実行されているのを確認できます。

index.html


<!DOCTYPE html>
<html lang="ja">

<head>
<meta charset="UTF-8">
<title>webpack Sample</title>

<script src="./app.js"></script>

</head>
<body>

<h1>webpack !!</h1>

</body>
</html>



webpackでCSSも読み込んでビルドすることが可能です。







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