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<!DOCTYPE html> <html> <head> <style> #ex1 { color: red; } </style> </head> <body> <h1>setProperty() 方法</h1> <p>单击该按钮可将新的 CSS 属性设置为 "important" 优先级。</p> <button onclick="myFunction()">试一试</button> <div id="ex1">一些文本。</div> <script> function myFunction() { var declaration = document.styleSheets[0].cssRules[0].style; var setprop = declaration.setProperty("background-color", "yellow", "important"); } </script> </body> </html>