Jquery: Checking to see if div contains text, then action

I'm trying to check in jQuery if a div contains some text, and then add a class if it does.

So I wrote something like this:

    if( $("#field > div.field-item").text().indexOf('someText') = 0) {
        $("#somediv").addClass("thisClass");
    }

I'm not getting this to work.

<div id="field"><div class="field-item">someText</div></div>

<div id="somediv"></div>

Is this incorrect?