How jQuery checks whether the check box is checked and an example

To enable this function today, you can assign a value to the input form when the check box is selected, and clear the form value when the check box is canceled.

Effect
 
Implementation source code: cyfID is the id of the check box
Copy codeThe Code is as follows:
$ ("# CyfID"). click (function (){
Var ischeck = $ (this). attr ("checked ");
If (ischeck = undefined ){
// Clear the input box
Alert ("");
} Else {
// Assign a value to the input box
Alert ("qq ");
}
});

Implementation principle: when the check box is checked, $ (this). attr ("checked") is checked and undefined is not checked.