# Opening a Popup

You can open up a Nosto behavioral pop-up by calling the `api.openPopup()` function. The first argument of the function is the ID of the popup campaign whose pop-up you want to show. The pop-up campaigns, including the pop-up templates themselves, are created in the Nosto Administration UI.

Please note that some campaigns have active trigger types and can be opened automatically. If you want to use only the `api.openPopup()` call to open pop-ups, please create the respective campaigns using the JavaScript API pop-up trigger type.

You can also give a second, optional argument to the `api.openPopup()` function. The second argument is an object with the following fields:

```javascript
nostojs(api => {
  var arrayOfPopupCampaigns = api.popupCampaigns();

  // arrayOfPopupCampaigns = [
  //   { id: "campaignId", name: "campaignName", type: "triggerType" },
  //   ...
  // ];

  var popupCampaignId = arrayOfPopupCampaigns[0].id;

  api.openPopup(popupCampaignId);

  // or

  var popupOptions = {
    // Effects corresponding to the ones in the admin UI
    effects: {
      overlayOpacity: 0.8,
      fadeInDelayMs: 300
    },
    preview: false
  };
  api.openPopup(popupCampaignId, popupOptions);  
});
```

## Parameters

| Field          | Type      | Default | Reason                                                                                                                                                                                                     |
| -------------- | --------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| effects        | Read-Only |         | Describes the effects that should be used displaying the pop-up. If given, overrides the effects set up for the campaign in the Nosto Administration. See below for the description of the effects object. |
| preview        | boolean   |         | If true, an actual discount coupon won’t be given and the pop-up display won’t count in the analytics. Use this to preview the pop-up on your site.                                                        |
| overlayOpacity | number    | 0.8     | How opaque, or non-transparent, the background should look like when showing the pop-up. Value can range from 0.0 to 1.0                                                                                   |
| fadeInDelayMs  | number    | 0       | How many milliseconds to take to fade in the pop-up.                                                                                                                                                       |