dynamically create bound datas with polymer - forms

Question

I would like to create a dynamic form using polymer, meaning that everytime the user press "add" button,it will add a new field in the form. Or, more specifically, it will add a paper-dropdown-menu, where all of the options come from a dom-repeat fed by an ajax call.
this is what i've done so far:
<div id="filterContainer">
<div class="flex rulesForm" id="filter1">
<paper-dropdown-menu name="rule1A" no-label-float>
<paper-listbox attr-for-selected="value" selected="{{filter1A}}" class="dropdown-content" id="thirdPartyFilter1A">
<template is="dom-repeat" items="{{rule1A}}">
<paper-item value="[[item]]">[[item]]</paper-item>
</template>
</paper-listbox>
</paper-dropdown-menu>
</div>
</div>
<paper-button raised on-tap="addFilterField">Add</paper-button>
<div>
and in the JS:
addFilterField: function () {
let dropdown = document.createElement('paper-dropdown-menu');
dropdown.name = "";
dropdown.noLabelFloat = true;
let listbox = document.createElement('paper-listbox');
listbox.class = "dropdown-content";
listbox.attrForSelected = "value";
listbox.selected = "{{filter1A}}";
let paperItem = document.createElement('paper-item');
paperItem.value = "[[item]]";
var itemNode = document.createTextNode('[[item]]');
paperItem.appendChild(itemNode);
listbox.appendChild(paperItem);
dropdown.appendChild(listbox);
console.log(dropdown);
filterContainer.appendChild(dropdown);
my problem is about the data-binding... If I use createTextNode with [[item]], it will simply write it as a string in the document. Is there a way to fix this? (or a way easier solution to add field in a form?)

Answer 1

first of all you cannot use binding notation in javascript. it is markup
2nd, polymer doesn't yet support creating data bindings dynamically. however I'm sure you can accomplish what you are trying to do.
3rd,
you have to use the Polymer Dom API. https://www.polymer-project.org/1.0/docs/devguide/local-dom#dom-api
instead of paperItem.appendChild(itemNode)
you would use
Polymer.dom(listbox).appendChild(itemNode);