Jquery checkbox checked when page loads

The script is working fine however I am wondering if there is a way to avoid the repetition in the code (DRY method).

Demo

JS code:

// Checkbox checked and input disbaled when page loads

$('#checkbox').prop('checked', true);

if ($('#checkbox').is(':checked') == true) {
    $('#textInput').prop('disabled', true);
}


// Enable-Disable text input when checkbox is checked or unchecked

$('#checkbox').change(function() {
    if ($('#checkbox').is(':checked') == true) {
        $('#textInput').prop('disabled', true);
    } else {
        $('#textInput').val('').prop('disabled', false);
    }
});