CODEWITHSUNDEEP
polymer
Peter
Peter

Reputation: 1710

How To Access Polymer Custom Element From Callback

I need to access the custom element and call its method from the click event callback.

<polymer-element name="my-element">
    <template>
        <style type="text/css" media="screen">
            ...
        </style>
        <ul id="my_data"></ul>
    </template>

    <script>
        Polymer('my-element', {
            dataSelected: function(selectedText) {
                //...
            },

            setData: function(data) {
                for (var i = 0; i < data.length; i++) {
                    var li = document.createElement('li');
                    li.addEventListener('click', function(e) {
                        // how can I call dataSelected() from here?
                    });
                    li.innerText = data[i];
                    this.$.my_data.appendChild(li);
                }
            }
        });
    </script>
</polymer-element>

How can I call the custom element's dataSelected() method from the callback?

Upvotes: 2

Views: 4008

Answers (2)

Scott Miles
Scott Miles

Reputation: 11027

You can use bind to attach a this context to any function, so:

   li.addEventListener('click', function(e) {
      this.dataSelected(e.target.innerText);
    }.bind(this));

http://jsbin.com/xorex/4/edit

But you can make things easier by using more Polymer sugaring. For example, you can publish data and use the observation system, like so:

<polymer-element name="my-element" attributes="data">
...
    data: [], // type hint that data is an array
...
    dataChanged: function() { // formerly setData

http://jsbin.com/xorex/5/edit

Also, you can use the built-in event system instead of addEventListener

<polymer-element name="my-element" attributes="data">
  ...
  <ul id="my_data" on-tap="{{dataTap}}"></ul>
  ...
    dataTap: function(e) { // `tap` supports touch and mouse
      if (e.target.localName === 'li') {
        this.dataSelected(e.target.textContent);
      }
    }

http://jsbin.com/xorex/6/edit

But the biggest win is using <template repeat> instead of creating elements in JavaScript. At that point, the complete element can look like this:

<polymer-element name="my-element" attributes="data">
<template>

  <ul id="my_data">
    <template repeat="{{item in data}}">
      <li on-tap="{{dataTap}}">{{item}}</li>
    </template>
  </ul>

</template>
<script>

  Polymer('my-element', {
    data: [],

    dataTap: function(e) {
      console.log('dataSelected: ' + e.target.textContent);
    }
  });

</script>
</polymer-element>

http://jsbin.com/xorex/7/edit

Upvotes: 17

Dirk Grappendorf
Dirk Grappendorf

Reputation: 3422

You could insert element = this; at the beginning of your setData() function and call element.dataSelected(); in the event handler.

But i think for what you want to achieve, you'd better use a repeat template (Iterative templates) and a direct binding to your click handler function (Declarative event mapping).

Upvotes: 4

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