How to dynamically create CSS class in JavaScript and apply?

I need to create a CSS stylesheet class dynamically in JavaScript and assign it to some HTML elements like - div, table, span, tr, etc and to some controls like asp:Textbox, Dropdownlist and datalist.

Is it possible?

It would be nice with a sample.

---

虽然我不确定为什么要用JavaScript创建CSS类，但下面是一个选项：

var style = document.createElement('style');
style.type = 'text/css';
style.innerHTML = '.cssClass { color: #F00; }';
document.getElementsByTagName('head')[0].appendChild(style);

document.getElementById('someElementId').className = 'cssClass';

---

Found a better solution, which works across all browsers.
Uses document.styleSheet to add or replace rules. Accepted answer is short and handy but this works across IE8 and less too.

function createCSSSelector (selector, style) {
  if (!document.styleSheets) return;
  if (document.getElementsByTagName('head').length == 0) return;

  var styleSheet,mediaType;

  if (document.styleSheets.length > 0) {
    for (var i = 0, l = document.styleSheets.length; i < l; i++) {
      if (document.styleSheets[i].disabled) 
        continue;
      var media = document.styleSheets[i].media;
      mediaType = typeof media;

      if (mediaType === 'string') {
        if (media === '' || (media.indexOf('screen') !== -1)) {
          styleSheet = document.styleSheets[i];
        }
      }
      else if (mediaType=='object') {
        if (media.mediaText === '' || (media.mediaText.indexOf('screen') !== -1)) {
          styleSheet = document.styleSheets[i];
        }
      }

      if (typeof styleSheet !== 'undefined') 
        break;
    }
  }

  if (typeof styleSheet === 'undefined') {
    var styleSheetElement = document.createElement('style');
    styleSheetElement.type = 'text/css';
    document.getElementsByTagName('head')[0].appendChild(styleSheetElement);

    for (i = 0; i < document.styleSheets.length; i++) {
      if (document.styleSheets[i].disabled) {
        continue;
      }
      styleSheet = document.styleSheets[i];
    }

    mediaType = typeof styleSheet.media;
  }

  if (mediaType === 'string') {
    for (var i = 0, l = styleSheet.rules.length; i < l; i++) {
      if(styleSheet.rules[i].selectorText && styleSheet.rules[i].selectorText.toLowerCase()==selector.toLowerCase()) {
        styleSheet.rules[i].style.cssText = style;
        return;
      }
    }
    styleSheet.addRule(selector,style);
  }
  else if (mediaType === 'object') {
    var styleSheetLength = (styleSheet.cssRules) ? styleSheet.cssRules.length : 0;
    for (var i = 0; i < styleSheetLength; i++) {
      if (styleSheet.cssRules[i].selectorText && styleSheet.cssRules[i].selectorText.toLowerCase() == selector.toLowerCase()) {
        styleSheet.cssRules[i].style.cssText = style;
        return;
      }
    }
    styleSheet.insertRule(selector + '{' + style + '}', styleSheetLength);
  }
}

Function is used as follows.

createCSSSelector('.mycssclass', 'display:none');

Note that even though function name is createClass it actually creates a selector. So dont forget to add .(period) before your class name. No need to mention that you can create other selectors too with this function.

---

Short answer, this is compatible "on all browsers" (specifically, IE8/7):

function createClass(name,rules){
    var style = document.createElement('style');
    style.type = 'text/css';
    document.getElementsByTagName('head')[0].appendChild(style);
    if(!(style.sheet||{}).insertRule) 
        (style.styleSheet || style.sheet).addRule(name, rules);
    else
        style.sheet.insertRule(name+"{"+rules+"}",0);
}
createClass('.whatever',"background-color: green;");

And this final bit applies the class to an element:

function applyClass(name,element,doRemove){
    if(typeof element.valueOf() == "string"){
        element = document.getElementById(element);
    }
    if(!element) return;
    if(doRemove){
        element.className = element.className.replace(new RegExp("b" + name + "b","g"));
    }else{      
        element.className = element.className + " " + name;
    }
}

Here's a little test page as well: https://gist.github.com/shadybones/9816763

The key little bit is the fact that style elements have a "styleSheet"/"sheet" property which you can use to to add/remove rules on.

链接地址: http://www.djcxy.com/p/89300.html

上一篇: 边距白色空间

下一篇: 如何在JavaScript中动态创建CSS类并应用？