function styleSheetToString(styleSheet) {
    var result = "";
    var rules = styleSheet.cssRules,
        rule;
    for (var i = 0; i < rules.length; i++) {
        rule = rules[i];
        if (rule instanceof CSSOM.CSSImportRule) {
            result += styleSheetToString(rule.styleSheet) + '\n';
        } else {
            result += rule.cssText + '\n';
        }
    }
    return result;
}
function styleSheetToString(styleSheet) {
    var result = "";
    var rules = styleSheet.cssRules,
        rule;
    for (var i = 0; i < rules.length; i++) {
        rule = rules[i];
        if (rule instanceof CSSOM.CSSImportRule) {
            result += styleSheetToString(rule.styleSheet) + '\n';
        } else {
            result += rule.cssText + '\n';
        }
    }
    return result;
}
function styleSheetToString ( styleSheet ) { var result = "" ; var rules = styleSheet . cssRules , rule ; for ( var i = 0 ; i < rules . length ; i ++ ) { rule = rules [ i ] ; if ( rule instanceof CSSOM . CSSImportRule ) { result += styleSheetToString ( rule . styleSheet ) + '\n' ; } else { result += rule . cssText + '\n' ; } } return result ; }
把 StyleSheet 的内容转换成 css 字符串
@param  {StyleSheet} styleSheet
@return {String} css 字符串
把 StyleSheet 的内容转换成 css 字符串