这是一种
exportStyles()方法的代码，该方法应返回一个CSS字符串，包括给定元素的所有内联和外部样式，默认值 除外 （这是主要困难）。
例如：
console.log(someElement.exportStyles());
由于您使用的是Chrome，因此我无需理会它与IE兼容。实际上，只需要浏览器支持该
getComputedStyle(element)方法即可。
Element.prototype.exportStyles = (function () { // Mapping between tag names and css default values lookup tables. This allows to exclude default values in the result. var defaultStylesByTagName = {}; // Styles inherited from style sheets will not be rendered for elements with these tag names var noStyleTags = {"base":true,"HEAD":true,"HTML":true,"meta":true,"NOframe":true,"NOscript":true,"PARAM":true,"script":true,"STYLE":true,"TITLE":true}; // This list determines which css default values lookup tables are precomputed at load time // Lookup tables for other tag names will be automatically built at runtime if needed var tagNames = ["A","ABBR","ADDRESS","AREA","ARTICLE","ASIDE","AUDIO","B","base","BDI","BDO","BLOCKQUOTE","BODY","BR","BUTTON","CANVAS","CAPTION","CENTER","CITE","CODE","COL","COLGROUP","COMMAND","DATALIST","DD","DEL","DETAILS","DFN","DIV","DL","DT","EM","EMBED","FIELDSET","FIGCAPTION","FIGURE","FONT","FOOTER","FORM","H1","H2","H3","H4","H5","H6","HEAD","HEADER","HGROUP","HR","HTML","I","Iframe","IMG","INPUT","INS","KBD","KEYGEN","LABEL","LEGEND","LI","link","MAP","MARK","MATH","MENU","meta","METER","NAV","NOBR","NOscript","OBJECT","OL","OPTION","OPTGROUP","OUTPUT","P","PARAM","PRE","PROGRESS","Q","RP","RT","RUBY","S","SAMP","script","SECTION","SELECT","SMALL","SOURCE","SPAN","STRONG","STYLE","SUB","SUMMARY","SUP","SVG","TABLE","TBODY","TD","textarea","TFOOT","TH","THEAD","TIME","TITLE","TR","TRACK","U","UL","VAR","VIDEO","WBR"]; // Precompute the lookup tables. for (var i = 0; i < tagNames.length; i++) { if(!noStyleTags[tagNames[i]]) { defaultStylesByTagName[tagNames[i]] = computeDefaultStyleByTagName(tagNames[i]); } } function computeDefaultStyleByTagName(tagName) { var defaultStyle = {}; var element = document.body.appendChild(document.createElement(tagName)); var computedStyle = getComputedStyle(element); for (var i = 0; i < computedStyle.length; i++) { defaultStyle[computedStyle[i]] = computedStyle[computedStyle[i]]; } document.body.removeChild(element); return defaultStyle; } function getDefaultStyleByTagName(tagName) { tagName = tagName.toUpperCase(); if (!defaultStylesByTagName[tagName]) { defaultStylesByTagName[tagName] = computeDefaultStyleByTagName(tagName); } return defaultStylesByTagName[tagName]; } return function exportStyles() { if (this.nodeType !== Node.ELEMENT_NODE) { throw new TypeError("The exportStyles method only works on elements, not on " + this.nodeType + " nodes."); } if (noStyleTags[this.tagName]) { throw new TypeError("The exportStyles method does not work on " + this.tagName + " elements."); } var styles = {}; var computedStyle = getComputedStyle(this); var defaultStyle = getDefaultStyleByTagName(this.tagName); for (var i = 0; i < computedStyle.length; i++) { var cssPropName = computedStyle[i]; if (computedStyle[cssPropName] !== defaultStyle[cssPropName]) { styles[cssPropName] = computedStyle[cssPropName]; } } var a = ["{"]; for(var i in styles) { a[a.length] = i + ": " + styles[i] + ";"; } a[a.length] = "}" return a.join("rn"); }})();
