javascript validation prevent certain words

I am trying to prevent users from entering in certain words and special characters into a text field like "and", "or", "/","\". How do I set a variable to two or more conditions, or how better should I approach this.

To start I was trying to prevent users from entering in "and" or or into the text field.

function watchForWords(text) {
  if (!text) {
  return true;
  }
  var isValid = (text.value != "and" || text.value != "or");
  if (!isValid) {
  text.style.backgroundColor = "#ff8";
  }
return isValid;
}