one or the other

by nabeezy

HTML

<input id="one" onkeyup="check()" />
<br/>
<input id="two" onkeyup="check()"/>

JavaScript

var one = $("#one");
var two = $("#two");
check = function(){
    if(one.val().length > 0){
        two.attr("disabled","disabled");
    }
    if(one.val().length == 0){
        two.attr("disabled",false);
    }
    if(two.val().length > 0){
        one.attr("disabled","disabled");
    }
    if(two.val().length == 0){
        one.attr("disabled",false);
    }  
};