动态样式类封装JS代码_javascript技巧

// CssRule类由StyleSheet.getRule方法返回，不直接创建
function CssRule(rule) {
this.rule = rule;
this.style = rule.style;
this.selectorText = rule.selectorText;
this.index = null;
}
function StyleSheet() {
var head = document.getElementsByTagName("head")[0];
//通过新建标签来创建新样式
/*
在此不用document.createStyleSheet来完成，是因为在FF下
如果未导入任何CSS文件的情况下document.createStyleSheet方法失败
*/
var style = document.createElement("style");
style.type = "text/css";
head.appendChild(style);
this.CatchStyle(document.styleSheets.length - 1);
}
StyleSheet.prototype = {
//可直接捕获现有Style
CatchStyle: function(index) {
this.style = document.styleSheets[index];
if (navigator.userAgent.indexOf("MSIE") < 0) { //非IE浏览器补丁
this.style.addRule = function(selector, style) {
var index = this.cssRules.length;
this.insertRule(selector + "{" + style + "}", index);
};
this.style.removeRule = function(index) {
this.deleteRule(index);
};
}
},
//新增样式
AddRule: function(selector, style) {
this.style.addRule(selector, style);
},
//删除样式
RemoveRule: function(index) {
this.style.removeRule(index);
},
//取得所有样式
getRules: function() {
if (this.style.rules) { //IE
return this.style.rules;
}
return this.style.cssRules; //非IE
},
//通过选择器，取得样式
getRule: function(selector) {
var rules = this.getRules();
for (var i = 0; i < rules.length; i++) {
var r = rules[i];
if (r.selectorText == selector) {
var rule = new CssRule(r);
rule.index = i;
return rule;
}
}
return null;
}
};

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