Q:

Add Argument to event-handler function?

I'm working with Polymer on a small web-project.
I'm displaying a delete button for every item in a list of items.
The delete button triggers the deleteItem()-function. I would like to add item.id or item itself as an argument so I can delete the right item.
How can I do this? 
<template id="bind" is="dom-bind">
  <script>
    var bind = document.querySelector('#bind');
    bind.deleteItem = function() {
      // Get item id?
    }
  </script>

  <template is="dom-repeat" items="{{data}}">
    <span>{{item.name}}</span>
    <paper-button on-click="deleteItem" id="{{item.id}}">Delete</paper-button></p>
  </template>
</template>

A:

You can't pass additional arguments to the event handler but you can get a reference to the model of the event.model.
See https://www.polymer-project.org/1.0/docs/devguide/templates.html#handling-events for an example
<dom-module id="simple-menu">

  <template>
    <template is="dom-repeat" id="menu" items="{{menuItems}}">
        <div>
          <span>{{item.name}}</span>
          <span>{{item.ordered}}</span> 
          <button on-click="order">Order</button>
        </div>
    </template>
  </template>

  <script>
    Polymer({
      is: 'simple-menu',
      ready: function() {
        this.menuItems = [
            { name: "Pizza", ordered: 0 },
            { name: "Pasta", ordered: 0 },
            { name: "Toast", ordered: 0 }
        ];
      },
      order: function(e) {
        var model = e.model; // <== get the model from the clicked item
        model.set('item.ordered', model.item.ordered+1);
      }
    });
  </script>

</dom-module>

