$(document).ready(function() {
    //copied from jquery-mobile
    var input = $("textarea#body"),
        extraLineHeight = 15,
        keyupTimeoutBuffer = 100,
        keyupTimeout;

    input._keyup = function() {
        var scrollHeight = input[ 0 ].scrollHeight,
        clientHeight = input[ 0 ].clientHeight;

        if ( clientHeight < scrollHeight ) {
            input.height( scrollHeight + extraLineHeight );
        }
    };

    input.on( "keyup change input paste", function() {
        clearTimeout( keyupTimeout );
        keyupTimeout = setTimeout( input._keyup, keyupTimeoutBuffer );
    });
});