jquery - Javascript: Combine function argument with string to reference var -

i have vars this:

var cardholder = $("#cardholder"); var cardholderinfo = $("#cardholder-info"); 

and function (which doesn't work) looks this:

function validaterequired(field){     //if it's not valid     if(field.val().length < 1){         field.addclass("field_error");         fieldinfo.text("(required)");         fieldinfo.addclass("error");          return false;     }     //if it's valid     else{         field.removeclass("field_error");         fieldinfo.text("");         fieldinfo.removeclass("error");         return true;     } } 

which access like:

cardholder.keyup(validaterequired(cardholder)); 

i've looked everywhere can't find need , i'm not sure should searching for.

i can use field value access straight cardholder var. want use field value reference cardholderinfo can manipulate element in function.

you call function this, passing second parameter:

cardholder.keyup(function () {     validaterequired(this, cardholderinfo); }); 

and modify function take second parameter:

function validaterequired(field, fieldinfo){     /* validation stuff */ }