我正在尝试使用Webpack Dev服务器来服务项目的前端。 我看到如果我使用样式加载器来处理css文件，则会收到此错误：
未定义窗口中的错误
我尝试通过以下检查来围绕窗口的引用来规避该问题：
if (typeof window !== 'undefined') {
我必须为检查而修改的样式加载器库中整个“ addStyle.js”的内容粘贴在下面。
/*
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
if (typeof window !== 'undefined' && typeof document !== 'undefined') {
return window && document && document.all && !window.atob;
}
});
var getTarget = function (target, parent) {
if (parent){
return parent.querySelector(target);
}
if (typeof document !== 'undefined') {
return document.querySelector(target);
}
};
var getElement = (function (fn) {
var memo = {};
return function(target, parent) {
// If passing function in options, then use it for resolve "head" element.
// Useful for Shadow Root style i.e
// {
// insertInto: function () { return document.querySelector("#foo").shadowRoot }
// }
if (typeof target === 'function') {
return target();
}
if (typeof memo[target] === "undefined") {
var styleTarget = getTarget.call(this, target, parent);
// Special case to return head of iframe instead of iframe itself
if (typeof window !== 'undefined') {
if (window.HTMLIFrameElement && styleTarget instanceof window.HTMLIFrameElement) {
try {
// This will throw an exception if access to iframe is blocked
// due to cross-origin restrictions
styleTarget = styleTarget.contentDocument.head;
} catch (e) {
styleTarget = null;
}
}
memo[target] = styleTarget;
}
}
return memo[target]
};
})();
var singleton = null;
var singletonCounter = 0;
var stylesInsertedAtTop = [];
var fixUrls = require("./urls");
module.exports = function(list, options) {
if (typeof DEBUG !== "undefined" && 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 && typeof options.singleton !== "boolean") 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 if (typeof options.insertAt === "object" && options.insertAt.before) {
var nextSibling = getElement(options.insertAt.before, target);
target.insertBefore(style, nextSibling);
} else {
throw new Error("[Style Loader]\n\n Invalid value for parameter 'insertAt' ('options.insertAt') found.\n Must be 'top', 'bottom', or Object.\n (https://github.com/webpack-contrib/style-loader#insertat)\n");
}
}
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) {
if (typeof document !== 'undefined') {
var style = document.createElement("style");
if (options.attrs.type === undefined) {
options.attrs.type = "text/css";
}
if (options.attrs.nonce === undefined) {
var nonce = getNonce();
if (nonce) {
options.attrs.nonce = nonce;
}
}
addAttrs(style, options.attrs);
insertStyleElement(options, style);
return style;
}
}
function createLinkElement (options) {
if (typeof document !== 'undefined') {
var link = document.createElement("link");
if (options.attrs.type === undefined) {
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 getNonce() {
if (typeof __webpack_nonce__ === 'undefined') {
return null;
}
return __webpack_nonce__;
}
function addStyle (obj, options) {
var style, update, remove, result;
// If a transform function was defined, run it on the css
if (options.transform && obj.css) {
result = typeof options.transform === 'function'
? options.transform(obj.css)
: options.transform.default(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 &&
typeof URL === "function" &&
typeof URL.createObjectURL === "function" &&
typeof URL.revokeObjectURL === "function" &&
typeof Blob === "function" &&
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 &&
newObj.media === obj.media &&
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) {
if (!style) {
return
}
var css = remove ? "" : obj.css;
if (style.styleSheet) {
style.styleSheet.cssText = replaceText(index, css);
} else {
if (typeof document !== 'undefined') {
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) {
if (!style) {
return
}
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);
}
if (typeof document !== 'undefined') {
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 && 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], { type: "text/css" });
var oldSrc = link.href;
link.href = URL.createObjectURL(blob);
if(oldSrc) URL.revokeObjectURL(oldSrc);
}
但是现在我收到另一个错误，提示app.css文件未返回任何字符串。
尽管仍然使用样式加载器来提供前端服务（即未定义Window错误不会阻止Webpack提供内容），但它禁用了热部署，这是我尝试实现此功能的主要原因。
感谢您的阅读！任何帮助，将不胜感激。