[javascript] Google Script to see if text contains a value

I have a google form that when the user submits it will trigger my function to run which is creating a summary of what they submitted as a Google Doc. I know it can automatically send an email but I need it formatted in a way that my user can edit it later.

There are some check boxes on the form -- but the getResponse() is only populated with the items checked and I need it to show all possible choices. Then I will indicate somehow what was checked.

I can't find a way to see if a text contains a value. Like in Java with a String, I could do either .contains("9th") or .indexOf("9th") >=0 and then I would know that the String contains 9th. How can I do this with google scripts? Looked all through documentation and I feel like it must be the easiest thing ever.

var grade = itemResponse.getResponse();

Need to see if grade contains 9th.

I used the Google Apps Script method indexOf() and its results were wrong. So I wrote the small function Myindexof(), instead of indexOf:

function Myindexof(s,text)
{
  var lengths = s.length;
  var lengtht = text.length;
  for (var i = 0;i < lengths - lengtht + 1;i++)
  {
    if (s.substring(i,lengtht + i) == text)
      return i;
  }
  return -1;
}

var s = 'Hello!';
var text = 'llo';
if (Myindexof(s,text) > -1)
   Logger.log('yes');
else
   Logger.log('no');

Update 2020:

You can now use Modern ECMAScript syntax thanks to V8 Runtime.

You can use includes():

var grade = itemResponse.getResponse();
if(grade.includes("9th")){do something}

I had to add a .toString to the item in the values array. Without it, it would only match if the entire cell body matched the searchTerm.

function foo() {
    var ss = SpreadsheetApp.getActiveSpreadsheet();
    var s = ss.getSheetByName('spreadsheet-name');
    var r = s.getRange('A:A');
    var v = r.getValues();
    var searchTerm = 'needle';
    for(var i=v.length-1;i>=0;i--) {
        if(v[0,i].toString().indexOf(searchTerm) > -1) {
            // do something
        }
    }
};