How do i change an attribute using jquery else

I'm using polymer, and jquery to change an attribute of a tag, if one tag's attribute is false, using an if/else statement, currently the one I am using doesn't work, how would I make it work? Here is what I have so far:

<p flex>Would you like notifications on?</p> <paper-toggle-button checked="false" id="onoff"></paper-toggle-button>
<p flex>Private Message Notifications?</p> <paper-toggle-button checked="true" id="pmn" class="blue"></paper-toggle-button>
<p flex>Game Update Notifications?</p> <paper-toggle-button checked="true" id="gun" class="lightgrey"></paper-toggle-button>
<p flex>Website Update Notifications?</p> <paper-toggle-button checked="true" id="wun" class="pink"></paper-toggle-button>
var main = document.querySelector('#onoff');
var pmn = document.querySelector('#pmn');
var wun = document.querySelector('#wun');
var gun = document.querySelector('#gun');

if ( $('#onoff').attr('checked') == 'true' ) {
    // do this
} else {
    pmn.removeAttribute("checked");
    wun.removeAttribute("checked");
    gun.removeAttribute("checked");
    pmn.setAttribute("disabled", "true");
    wun.setAttribute("disabled", "true");
    gun.setAttribute("disabled", "true");

}

I currently have #onoff checked="false" so the other toggles would automatically be disabled and the attribute checked would equal false, but it doesn't, anyone can tell me what I'm doing wrong, and how to fix it?