자바스크립트로 CSS 스타일을 수정하는 방법

element.style.height = '100px';

element.setAttribute('height', 100);
element.setAttribute('height', '100px');

element.setAttribute('style', 'height: 100px !important');

element.style.setProperty('height', '300px', 'important');

element.className = 'blue';
element.className += 'blue fb';

element.style.cssText = 'height: 100px !important';
element.style.cssText += 'height: 100px !important';

  function addNewStyle(newStyle) {
            var styleElement = document.getElementById('styles_js');

            if (!styleElement) {
                styleElement = document.createElement('style');
                styleElement.type = 'text/css';
                styleElement.id = 'styles_js';
                document.getElementsByTagName('head')[0].appendChild(styleElement);
            }
            
            styleElement.appendChild(document.createTextNode(newStyle));
        }

        addNewStyle('.box {height: 100px !important;}');

// 在原有样式操作
        document.styleSheets[0].addRule('.box', 'height: 100px');
        document.styleSheets[0].insertRule('.box {height: 100px}', 0);

        // 或者插入新样式时操作
        var styleEl = document.createElement('style'),
            styleSheet = styleEl.sheet;

        styleSheet.addRule('.box', 'height: 100px');
        styleSheet.insertRule('.box {height: 100px}', 0);

        document.head.appendChild(styleEl);