Tutorial :Creating a CSS class in jQuery



Question:

I believe the .addClass() function in jQuery attaches a CSS class to the current selection, but I was wondering I could create or define a CSS class in jQuery, and then attach it?


Solution:1

Actually, you can create a CSS rule that will affect all elements on the current page. In most browsers it should be as simple as:

var style = $('<style>body { background: green; }</style>')  $('html > head').append(style);  

This may or may not work in IE, however you can use IE's proprietary addRule instead:

document.styleSheets[0].addRule('body', 'background: green', -1);  

Naturally this will not assist you in creating css files that can be shared between webpages, but it is a handy way of affecting the style of a large number of elements without the need to iterate over them.


Solution:2

I'm not exactly sure what you want, but I think the best you can do is something like this:

var someClass = { "width": "100%", "background": "#ffffff" };  $(this).css(someClass);  

Note that this is not actually creating a class, but it might do what you need.


Solution:3

Here's something that will create a CSS class that will be available everywhere and apply it to a jQuery object. This uses the same basic technique as mentioned by MooGoo but is fleshed out into a fully functional piece of code:

(function() {      var addRule;        if (typeof document.styleSheets != "undefined" && document.styleSheets) {          addRule = function(selector, rule) {              var styleSheets = document.styleSheets, styleSheet;              if (styleSheets && styleSheets.length) {                  styleSheet = styleSheets[styleSheets.length - 1];                  if (styleSheet.addRule) {                      styleSheet.addRule(selector, rule)                  } else if (typeof styleSheet.cssText == "string") {                      styleSheet.cssText = selector + " {" + rule + "}";                  } else if (styleSheet.insertRule && styleSheet.cssRules) {                      styleSheet.insertRule(selector + " {" + rule + "}", styleSheet.cssRules.length);                  }              }          }      } else {          addRule = function(selector, rule, el, doc) {              el.appendChild(doc.createTextNode(selector + " {" + rule + "}"));          };      }        var createCssClass = function(className, cssProps, doc) {          doc = doc || document;            var head = doc.getElementsByTagName("head")[0];          if (head && addRule) {              var selector = "*." + className;              var ruleBits = [];              for (var i in cssProps) {                  if (cssProps.hasOwnProperty(i)) {                      ruleBits.push(i + ":" + cssProps[i] + ";");                  }              }              var rule = ruleBits.join("");              var styleEl = doc.createElement("style");              styleEl.type = "text/css";              styleEl.media = "screen";              head.appendChild(styleEl);              addRule(selector, rule, styleEl, doc);              styleEl = null;          }      };        jQuery.fn.createAndApplyCssClass = function(className, cssProps) {          createCssClass(className, cssProps, document);          this.addClass(className);      };  })();    $("#someelement").createAndApplyCssClass("test", {      "background-color": "green",      "color" : "white"  });  


Solution:4

With jQuery.Rule you can write code like this to append a new CSS rule:

$.rule('#content ul{ border:1px solid green }').appendTo('style');  

Extending a rule:

$.rule('#content ul', 'style').append('background:#FF9');  

Removing the whole rule:

$.rule('#content ul', 'style').remove();  

There is more in the API docs.

Internally, it uses the "append stylesheet to head" trick that MooGoo mentioned as well.


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