Function on Javascript. Not work -

i have file .js 1 function. , starting class want call function. not know why, function returns nothing. code have follows:

//valida data inserida pelo utilizador. function validardata(){     var datavalor = window.document.forms[0].data.value;     if(datavalor == ''){ //verifica se o campo data está preenchido         alert('o campo data encontra-se vazio. seleccione uma data!');         return false;     }else{         var t = validar(datavalor);         alert(t);         return false;     } } 

the code in file .js is:

function validar(data){     return data; } 

does have idea why not work?

without accompanying html go off of, answer shooting in dark.. but, provided attach function submit event, returning value of function...

<form onsubmit="return validardata();"> <!--                   ^ - in submit event(just listing way simple explanation instead of advanced event attaching) --> 

and provided functions defined in document head, or body, code works fine me:

<form method="post" onsubmit="return validardata()">     <input type="text" name="data" />     <input type="submit" /> </form> 

//valida data inserida pelo utilizador. function validardata(){     var datavalor = window.document.forms[0].data.value;     console.log(datavalor);     if(datavalor == ''){ //verifica se o campo data está preenchido         alert('o campo data encontra-se vazio. seleccione uma data!');         return false;     }else{         var t = validar(datavalor);         alert(t);         return false;     } }  function validar(data){     return data; } 

of course, that's assuming correctly link functions if exist in other files..

<script type='text/javascript' src='path/to/script.js'></script>