1

I'm perfectly aware that jQuery has css() method which allows me to modify the style specified elements. However I want to modify rules within a stylesheet on the go. It has some legit uses which the css() method cannot replace.

Something like:

<style id="dyn-style">
    p{ color:black; }
</style>
<p>TEST</p>
<script>
    $('#dyn-style').getCssRule('p').alterRule('color', 'red');
</script>

Which then changes the content of the style element to this:

<style id="dyn-style">
    p{ color:red; }
</style>

I searched a bit, but only found this solution. From what I understand, it only adds new style elements (with defined styles) rather than alter existing ones.

I'm tempted to write a plugin on my own, but it would be pointless to do so if one exists already.

  • I don't think you can do this in jQuery. The reason is that in many browsers, javascript cannot access all of the style sheets; you get an access violation for cross-domain, etc. ... But, if you just want to muck with inline <style> elements, that would be possible but it also be a pretty limited plugin. ... The Smart way to do things is to have one hosted (and cached) CSS file that has alternate classes. jQuery then adds and removes classes as desired. This would also give a performance boost over (re)writing styles. – Brock Adams Oct 5 '14 at 7:29
1

I couldn't find such plugin, so I wrote my own jquery-style. After I finished writing the plugin I wanted to name it jQuery StyleSheet, but it turns out there was already a plugin under that name and said plugin does exactly what I wanted...

Anyway the other jQuery StyleSheet plugin can be found at jQuery Repository and GitHub.

The author of jQuery StyleSheet also mentions something called YUI StyleSheet utility, which might offer to do more or less the same.

Edit: To prevent this answer from being a link only one, here is the code of my plugin. Note, this is published under WTFPL license. There might be some bugs in this too...

(function($) {
    // cssNameToJsName(name) - Converts style name in css format to camel case format used by javascript
    //
    // background-color => backgroundColor
    function cssNameToJsName(name)
    {
        var split = name.split("-");
        var output = "";
        for(var i = 0; i < split.length; i++)
        {
            if (i > 0 && split[i].length > 0 && !(i == 1 && split[i] == "ms"))
            {
                split[i] = split[i].substr(0, 1).toUpperCase() + split[i].substr(1);
            }
            output += split[i];
        }
        return output;
    }

    // jsNameToCssName(name) - Converts style name in javascript camel case format to css format; NOT USED
    //
    // backgroundColor => background-color
    function jsNameToCssName(name)
    {
        return name.replace(/([A-Z])/g, "-$1").toLowerCase();
    }

    // Rule - Object storing list of rules within stylesheets matching (=) provided selector
    //
    // Fields:
    // length - number of rules in the list
    // [i] - a single rule within the list (indexing has no relation to the indexing within the stylesheet)
    //
    // Methods:
    // css() - Alters style within rules or returns the value of the first specified style within a rule
    // each() - executes provided function for all rules within the list
    // remove() - removes rules in the list
    //
    // new Rule (name, sheet) - creates a new list of rules matching provided selector
    // name - rule selector
    // sheet - list of styles (Sheet object)
    //
    // new Rule (name, sheet, index) - creates a new list of rules matching provided selector and matching provided index within the parent stylesheet
    // name - rule selector
    // sheet - list of styles (Sheet object)
    // index - index filter
    function Rule (name, sheet, index)
    {
        this.length = 0;
        var self = this;
        sheet.each(function()
        {
            // ie<9 hack
            var rules = null;
            if (typeof this.cssRules == 'undefined')
            {
                rules = this.rules;
            }
            else
            {
                rules = this.cssRules;
            }
            for (var i = 0; i < rules.length; i++)
            {
                if (rules[i].selectorText == name && (typeof index == 'undefined' || i == index))
                {
                    self[self.length] = rules[i]
                    self[self.length].index = i;
                    self.length++;
                }
            }
        });
    }

    // Alters style within rules or returns the value of the first specified style within a rule
    //
    // Rule.css(name) - returns value of specified style from the first rule in the list
    // name - style name in css format (for example "background-color")
    //
    // Example: $('#my-style').styleSheet().rule('p').css('color')
    //
    // Rule.css(name, value) - set specified style to provided value for all rules within the list
    // name - style name in css format
    // value - new value for specified style
    //
    // Example: $('#my-style').styleSheet().rule('p').css('color', 'red')
    //
    // Rule.css(name, value, index) - set specified style to provided value for rules matching provided index within the parent stylesheet
    // name - style name in css format
    // value - new value for specified style
    // index - rule index
    //
    // Example: $('#my-style').styleSheet().rule('p').css('color', 'red', 0)
    //
    // Rule.css(data) - set multiple styles for all rules in the list using an object (for example {'color' : 'red', 'font-weight' : 'bold'})
    // data - object containing style name and value pairs
    //
    // Example: $('#my-style').styleSheet().rule('p').css({'color' : 'red', 'font-weight' : 'bold'})
    //
    // Rule.css(data, index) - set multiple styles for all rules matching provided index within the parent stylesheet
    // data - object containing style name and value pairs
    // index - rule index
    //
    // Example: $('#my-style').styleSheet().rule('p').css({'color' : 'red', 'font-weight' : 'bold'}, 0)
    Rule.prototype.css = function() {
        var name = null;
        var data = null;
        var value = null;
        var index = null;
        // check function arguments to determine which where provided
        if (typeof arguments[0] == 'object')
        {
            data = arguments[0];
            if (arguments.length > 1)
            {
                index = arguments[1];
            }
        }
        else
        {
            name = arguments[0];
            if (arguments.length > 1)
            {
                value = arguments[1];
            }
            if (arguments.length > 2)
            {
                index = arguments[2];
            }
        }
        // check if set value or data was specified and if not return value of first matching style within the first rule in the list
        if (value == null && name != null)
        {
            if (this.lenght == 0)
                return null;

            return this[0].style[cssNameToJsName(name)];
        }
        // determin if we are setting multiple styles or just one
        if (data != null)
        {
            // if data object was provided, map its properties to styles
            this.each(function()
            {
                for (var key in data)
                {
                    // optional index filter
                    if (index == null || this.index == index)
                        this.style[cssNameToJsName(key)] = data[key]
                }
            });
        }
        else
        {
            // if name and value were provided, set them
            this.each(function()
            {
                // optional index filter
                if (index == null || this.index == index)
                    this.style[cssNameToJsName(name)] = value;
            });
        }
        return this;
    };

    // Rule.each(func) - executes provided function for all rules within the list
    // func - function to be executed
    Rule.prototype.each = function(func) {
        for(var i = 0; i < this.length; i++){
            func.apply(this[i], [this[i], i]);
        }
        return this;
    };

    // Rule.remove() - removes all rules in the list
    //
    // Rule.remove(index) - removes rules matching specified index within the parent stylesheet
    Rule.prototype.remove = function(index) {
        this.each(function()
        {
            if (typeof index == 'undefined' || this.index == index)
            {
                // ie<9 hack
                if (typeof this.parentStyleSheet.deleteRule == 'undefined')
                {
                    this.parentStyleSheet.removeRule(this.index);
                }
                else
                {
                    this.parentStyleSheet.deleteRule(this.index);
                }
            }
        });
    };

    // Sheet - Object storing list of stylesheets
    //
    // Fields:
    // elements - jquery style list of elements
    // length - number of stylesheets in the list
    // [i] - a single stylesheed within the list
    //
    // Methods:
    // each() - executes provided function for all rules within the list
    // rule() - returns a list of rules matching (=) provided selector within the stylesheet list
    // addRule() - adds a rule to stylesheets in the list
    //
    // new Sheet(elements) - creates a new stylesheet list from provided elements (element of type different than "style" will be ignored)
    // elements - jquery style list of elements
    //
    // Example: new Sheet($('style'))
    function Sheet (elements) {
        this.element = elements.find('style');
        this.length = 0;
        var self = this;
        elements.each(function()
        {
            self[self.length] = this.sheet;
            self.length++;
        });
    }

    // Sheet.rule() - returns list of rules with matching selector (=) from provided "style" elements (elements other than "style" are ignored)
    //
    // Sheet.rule(name) - returns list of rules with matching selector (=) from provided "style" elements
    // name - rule selector to match
    //
    // Example: $('#my-stylesheet').styleSheet().rule('p')
    //
    // Sheet.rule(name, index) - returns list of rules with matching selector (=) from provided "style" elements; also filtered by index within the parent stylesheet
    // name - rule selector to match
    // index - index within the parent stylesheet
    //
    // Example: $('#my-stylesheet').styleSheet().rule('p', 0)
    Sheet.prototype.rule = function(name, index) {
        return new Rule (name, this);
    };

    // Sheet.each(func) - executes provided function for all stylesheets within the list
    // func - function to be executed
    Sheet.prototype.each = function(func) {
        for(var i = 0; i < this.length; i++){
            func.apply(this[i], [this[i], i]);
        }
        return this;
    };

    // Sheet.addRule(name, style) - adds provided rule to all stylesheets in the list as the last rule in the stylesheet
    // name - rule selector
    // style - rule styles as a string or style name and value pair object
    //
    // Example: $('#my-stylesheet').styleSheet().addRule('p', 'color: red; font-weight: bold')
    // Example: $('#my-stylesheet').styleSheet().addRule('p', {'color': 'red', 'font-weight': 'bold'})
    //
    // Rule.addRule(name, style, index) - inserts provided rule to all stylesheets in the list in specified position
    // name - rule selector
    // style - rule styles as a string or style name and value pair object
    // index - position of the inserted rule within the stylesheet
    Sheet.prototype.addRule = function(name, style, index) {
        this.each(function()
        {
            var oldIe = typeof this.cssRules == 'undefined';
            if (typeof index == 'undefined')
            {
                // ie<9 hack
                var rules = null;
                if (oldIe)
                {
                    rules = this.rules;
                }
                else
                {
                    rules = this.cssRules;
                }
                index = rules.length;
            }
            var styleStr = "";
            if (typeof style == 'object')
            {
                for (var key in style)
                {
                    styleStr += key + ": " + style[key] + ";";
                }
            }
            else
            {
                styleStr = style;
            }
            if (oldIe)
            {
                this.addRule(name, styleStr, index);
            }
            else
            {
                styleStr = name + " {" + styleStr + "}";
                this.insertRule(styleStr, index);
            }
        });
        return this;
    };

    // styleSheet - returns list of stylesheets ("style" elements) from within the provided elements
    //
    // Example: $('#my-stylesheet').styleSheet()
    $.fn.styleSheet = function() {
        return new Sheet (this);
    };

    // wrapper for styleSheet().rule(name, index)
    $.fn.cssRule = function(name, index) {
        return styleSheet().rule(name, index);
    };

    // wrapper for styleSheet().addRule(name, style, index)
    $.fn.addCssRule = function(name, style, index) {
        return styleSheet().addRule(name, style, index);
    };

    // wrapper for styleSheet().rule(name, index).remove();
    $.fn.removeCssRule = function(name, index) {
        return styleSheet().rule(name, index).remove();
    };
})(jQuery);

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