Modification of dom-if to be if/else compliant.
This is a Polymer Element providing the missing ELSE portion for the "DOM-IF" template by way of an alterative to DOM-IF.
bower install --save dom-if-else
<button onclick="clicked()">Toggle</button>
<template id="domIf" is="dom-if-else" if>
<if-then>
<div>1</div>
<div>2</div>
<div>3</div>
Stuff
<div>4</div>
</if-then>
<if-else>
<div>e1</div>
<div>e2</div>
More stuff
<div>e3</div>
</if-else>
</template>
<script>
function clicked() {
var t=document.querySelector('#domIf');
t.set('if',!t.if);
}
</script>