"var select = document.getElementById(Select1)[0];//找到下来框"以下2处改成var select = document.getElementByName("Select1")[0];//找到下来框<select id="Select1" name ="Select1" style="width: 200px" onchange ="setScreenWidth()">
调试欢乐多
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var select = document.getElementById(Select1)[0];//找到下来框改成
var select = document.getElementById("Select1");//找到下来框