How to dynamically create CSS class in JavaScript and apply?

Question

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,

Answer 1

https://jsfiddle.net/xk6Ut/256/

One option to dynamically create and update CSS class in JavaScript:

• Using Style Element to create a CSS section
• Using an ID for the style element so that we can update the CSS
  class

.....

function writeStyles(styleName, cssText) {
    var styleElement = document.getElementById(styleName);
    if (styleElement) 
             document.getElementsByTagName('head')[0].removeChild(
        styleElement);
    styleElement = document.createElement('style');
    styleElement.type = 'text/css';
    styleElement.id = styleName;
    styleElement.innerHTML = cssText;
    document.getElementsByTagName('head')[0].appendChild(styleElement);
}

...

    var cssText = '.testDIV{ height:' + height + 'px !important; }';
    writeStyles('styles_js', cssText)