W3School TIY Editor
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<!DOCTYPE html> <html> <body> 复选框：<input type="checkbox" id="myCheck"> <p>单击按钮可设置或返回复选框的不确定状态。</p> <button onclick="myFunction()">返回状态</button> <button onclick="myFunction2()">设置状态</button> <p id="demo"></p> <script> function myFunction() { var x = document.getElementById("myCheck").indeterminate; document.getElementById("demo").innerHTML = x; } function myFunction2() { var x = document.getElementById("myCheck").indeterminate = true; } </script> </body> </html>