Compare array of words to a textarea input with javascript

Question

I have a textarea inside a form.

Before the form is submitted, the textarea is validated and checked so it is not empty, not over 2000 characters, not contain forbid

Answer 1

var bad_words = new Array('word1', 'word2');
var user_words = document.getElementById('textarea').split(/\W+/);

for( var i in bad_words)
{
  if( user_words.indexOf( bad_words[i] ) != -1 )
  {
    alert( 'The textarea has bad word!');
    break;
  }
}