How to modify css style with javascript

Modification method: 1. Use "Element.style.Attribute name="value""; 2. Use "Element.setAttribute('Attribute name','Value')"; 3. Use "Element. setAttribute('style','Attribute name: value')"; 4. Use "element.className='value'".

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

1. Directly set the attribute of style In some cases, use this setting! important value is invalid

If the attribute has a '-' sign, write it in camel case (such as textAlign) If you want to retain the - sign, use the form of square brackets element.style['text-align'] = '100px';

element.style.height = '100px';

2. Set the attribute directly (can only be used For some attributes, related styles will be automatically recognized)

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

3. Set the attributes of style

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

4. Use setProperty If you want to set !important, it is recommended to use this method to set the third parameter

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

5. Change class, such as JQ’s change class related method

Because JS cannot obtain the pseudo-element of css, so you can dynamically change the style of the pseudo-element by changing the class of the pseudo-element's parent

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

6. Set cssText

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

7. Create and introduce new css style files

  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;}');

8. Use addRule and insertRule

// 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);

[Recommended learning: javascript Advanced Tutorial】

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