jQuery detect if string contains something

You get the value of the textarea, use it :

$('.type').keyup(function() {
    var v = $('.type').val(); // you'd better use this.value here
    if (v.indexOf('> <')!=-1) {
       console.log('contains > <');        
    }
});

use Contains of jquery Contains like this

if ($('.type:contains("> <")').length > 0)
{
 //do stuffs to change 
}

You can use javascript's indexOf function.

var str1 = "ABCDEFGHIJKLMNOP";
var str2 = "DEFG";
if(str1.indexOf(str2) != -1){
   alert(str2 + " found");
}

You could use String.prototype.indexOf to accomplish that. Try something like this:

$('.type').keyup(function() {
  var v = $(this).val();
  if (v.indexOf('> <') !== -1) {
    console.log('contains > <');
  }
  console.log(v);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea class="type"></textarea>

Update

Modern browsers also have a String.prototype.includes method.