add in error red border

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jQuery

im wondering how am i going to add in the red border

js

var fullname_msg = 'Please enter your name here!';
$("#fullname").keyup(function(){
    ("#fullname",fullname_msg)
});

html

<input class="inputText" type="text" id="fullname" name="fullname" value="" placeholder="NAME" />

CSS

.error {
	border:2px solid #ef716d !important;
}

i tried js
----------------------------------------

var fullname_msg = 'Please enter your name here!';
$("#fullname").keyup(function(){
    ("#fullname",fullname_msg)
    });
$("#fullname").css('border-color', 'red');

------------------------------

var fullname_msg = 'Please enter your name here!';
$("#fullname").keyup(function(){
    ("#fullname",fullname_msg)
    });
$("#fullname").addClass('error');

all these are not working i not sure why?