在JavaScript/jQuery中解析CSS

Question

我正在尝试在JavaScript中实现CSS的解析,以便:

a {
  color: red;
}

被解析为对象:

{
  'a' {
    'color': 'red'
  }
}

首先,我可以使用JavaScript/jQuery 库吗？

我的实现非常基础,所以我确信它无论如何都不是万无一失的.例如,它适用于基本CSS,但对于类型的属性:

background: url(data:image/png;base64, ....);

它失败了,因为我split(';')用来分隔property:value对.在这里,;发生在value,所以它也在那一点分裂.

还有另一种方法吗？

这是代码:

parseCSS: function(css) {
    var rules = {};
    css = this.removeComments(css);
    var blocks = css.split('}');
    blocks.pop();
    var len = blocks.length;
    for (var i = 0; i < len; i++)
    {
        var pair = blocks[i].split('{');
        rules[$.trim(pair[0])] = this.parseCSSBlock(pair[1]);
    }
    return rules;
},

parseCSSBlock: function(css) { 
    var rule = {};
    var declarations = css.split(';');
    declarations.pop();
    var len = declarations.length;
    for (var i = 0; i < len; i++)
    {
        var loc = declarations[i].indexOf(':');
        var property = $.trim(declarations[i].substring(0, loc));
        var value = $.trim(declarations[i].substring(loc + 1));

        if (property != "" && value != "")
            rule[property] = value;
    }
    return rule;
},

removeComments: function(css) {
    return css.replace(/\/\*(\r|\n|.)*\*\//g,"");
}

谢谢!

Answer 1

您可以轻松使用浏览器自己的CSSOM来解析CSS:

var rulesForCssText = function (styleContent) {
    var doc = document.implementation.createHTMLDocument(""),
        styleElement = document.createElement("style");

   styleElement.textContent = styleContent;
    // the style will only be parsed once it is added to a document
    doc.body.appendChild(styleElement);

    return styleElement.sheet.cssRules;
};

对于返回的每个规则,您可以查看其中的属性rule.style.有关示例,请参见http://jsfiddle.net/v2JsZ/.

Answer 2

有一个用Javascript编写的CSS解析器叫做JSCSSP

Answer 3

要编写最傻瓜式的解析器,请遵循规范中定义的标记化和CSS 语法的确切规则.请注意,您不必通过墨水实现规范.您可以从最有可能遇到的小部件和CSS开始,然后从那里扩展.更好的是,完全跳过整个过程并使用@ Matthew的解决方案,除非这是一个学习练习.

有各种lexical扫描程序和解析器生成器可用于JavaScript.整个语法可以在w3的网站上找到.当你可以简单地使用它和解析器生成器在JavaScript中生成解析器时,为什么要重新工作.

1. Jison
2. Peg.js
3. Cruiser.Parse
4. McLexer
5. JS/CC

CSS的生产规则如下.

stylesheet
  : [ CHARSET_SYM STRING ';' ]?
    [S|CDO|CDC]* [ import [ CDO S* | CDC S* ]* ]*
    [ [ ruleset | media | page ] [ CDO S* | CDC S* ]* ]*
  ;
import
  : IMPORT_SYM S*
    [STRING|URI] S* media_list? ';' S*
  ;
media
  : MEDIA_SYM S* media_list LBRACE S* ruleset* '}' S*
  ;
media_list
  : medium [ COMMA S* medium]*
  ;
medium
  : IDENT S*
  ;
page
  : PAGE_SYM S* pseudo_page?
    '{' S* declaration? [ ';' S* declaration? ]* '}' S*
  ;
pseudo_page
  : ':' IDENT S*
  ;
operator
  : '/' S* | ',' S*
  ;
combinator
  : '+' S*
  | '>' S*
  ;
unary_operator
  : '-' | '+'
  ;
property
  : IDENT S*
  ;
ruleset
  : selector [ ',' S* selector ]*
    '{' S* declaration? [ ';' S* declaration? ]* '}' S*
  ;
selector
  : simple_selector [ combinator selector | S+ [ combinator? selector ]? ]?
  ;
simple_selector
  : element_name [ HASH | class | attrib | pseudo ]*
  | [ HASH | class | attrib | pseudo ]+
  ;
class
  : '.' IDENT
  ;
element_name
  : IDENT | '*'
  ;
attrib
  : '[' S* IDENT S* [ [ '=' | INCLUDES | DASHMATCH ] S*
    [ IDENT | STRING ] S* ]? ']'
  ;
pseudo
  : ':' [ IDENT | FUNCTION S* [IDENT S*]? ')' ]
  ;
declaration
  : property ':' S* expr prio?
  ;
prio
  : IMPORTANT_SYM S*
  ;
expr
  : term [ operator? term ]*
  ;
term
  : unary_operator?
    [ NUMBER S* | PERCENTAGE S* | LENGTH S* | EMS S* | EXS S* | ANGLE S* |
      TIME S* | FREQ S* ]
  | STRING S* | IDENT S* | URI S* | hexcolor | function
  ;
function
  : FUNCTION S* expr ')' S*
  ;
/*
 * There is a constraint on the color that it must
 * have either 3 or 6 hex-digits (i.e., [0-9a-fA-F])
 * after the "#"; e.g., "#000" is OK, but "#abcd" is not.
 */
hexcolor
  : HASH S*
  ;