JQuery 判断复选框是否选中

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$("input").attr("checked") == "checked" or "undefined"   $("input").prop("checked") == true or false

　　这种可以 

博客园找到一个沙雕博主骗人 骗我用这种 不可以 

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//$("input").prop("checked")                   //可以             if ($("#IsBuyGiveFund").prop("checked") == true)             {                 $('#BuyGiveFundAmount').removeAttr("readonly");               }             else {                 $('#BuyGiveFundAmount').val("");                 $('#BuyGiveFundAmount').attr("readonly", "readonly");             }               //不可以             //if ($("#IsBuyGiveFund").attr("checked") == true)             //{             //    $('#BuyGiveFundAmount').removeAttr("readonly");                              //}             //else             //{             //    $('#BuyGiveFundAmount').val("");             //    $('#BuyGiveFundAmount').attr("readonly", "readonly");             //}