true

needle

 haystack

inArray('find_me', ['text1', 'text2', 'find_me', 'text3']);

function inArray(needle, haystack) {
  var length = haystack.length;
  for(var i = 0; i < length; i++) {
      if(haystack[i] === needle) { return true };
  }
  return false;
}