UV API

This is for:

Developer

In this article, we’ll introduce you to the UV API, what it’s used for, and how to set it up and use it.

What is the UV API?

The Universal Variable API is a global event emitter used to pass underlying page or view information to third-party scripts. Using the UV API script, all data is exposed as events using window.uv. All events must conform to schemas defined in the QProtocol schemas.

Setting up and using the UV API

The UV API should be included as an inline script on the webpage at the top of head, immediately after the <meta charset... /> tag. By embedding the API in the head synchronously, any script in the page is able to emit or handle events without polling or waiting for asynchronous scripts to load.

Note

The UV API script can only be imported in IE8+, Firefox, Opera, Chrome, and Safari.

The following piece of code shows how to import the script:

<script>
!function(){function n(){function n(n){p.level=n}function e(n,e){p.info(n,"event emitted"),e=c(e||{}),e.meta=e.meta||{},e.meta.type=n,u.push(e),r(),v.listeners=f(v.listeners,function(n){return!n.disposed})}function o(n,e,o){function r(){return p.info("Replaying events"),t(function(){s(v.events,function(t){c.disposed||l(n,t.meta.type)&&e.call(o,t)})}),f}function i(){return p.info("Disposing event handler"),c.disposed=!0,f}p.info("Attaching event handler for",n);var c={type:n,callback:e,disposed:!1,context:o||window};v.listeners.push(c);var f={replay:r,dispose:i};return f}function t(n){p.info("Calling event handlers"),a++;try{n()}catch(n){p.error("UV API Error",n.stack)}a--,r()}function r(){if(0===u.length&&p.info("No more events to process"),u.length>0&&a>0&&p.info("Event will be processed later"),u.length>0&&0===a){p.info("Processing event");var n=u.shift();v.events.push(n),t(function(){s(v.listeners,function(e){if(!e.disposed&&l(e.type,n.meta.type))try{e.callback.call(e.context,n)}catch(n){p.error("Error emitting UV event",n.stack)}})})}}function i(n,e,o){var t=v.on(n,function(){e.apply(o||window,arguments),t.dispose()});return t}function s(n,e){for(var o=n.length,t=0;t<o;t++)e(n[t],t)}function c(n){var e={};for(var o in n)n.hasOwnProperty(o)&&(e[o]=n[o]);return e}function l(n,e){return"string"==typeof n?n===e:n.test(e)}function f(n,e){for(var o=n.length,t=[],r=0;r<o;r++)e(n[r])&&t.push(n[r]);return t}var u=[],a=0,p={info:function(){p.level>n.INFO||console&&console.info&&console.info.apply(console,arguments)},error:function(){p.level>n.ERROR||console&&console.error&&console.error.apply(console,arguments)}};n.ALL=0,n.INFO=1,n.ERROR=2,n.OFF=3,n(n.ERROR);var v={on:o,emit:e,once:i,events:[],listeners:[],logLevel:n};return v}"object"==typeof module&&module.exports?module.exports=n:window&&void 0===window.uv&&(window.uv=n())}();
</script>

Emit events

Emit

By embedding the API in the head synchronously, any script in the page is able to emit or handle events without polling or waiting for asynchronous scripts to load. See Coveo Experimentation Hub scripts for more information.

To emit events, call the uv.emit method on the UV API script by making the following call: uv.emit(type, [data]). The events sent with the UV API script are known as QProtocol events. See ecommerce - QProtocol events for a complete list of the ecommerce events that are defined by this protocol. The uv.emit method creates an event with the type and data specified. The data should conform to the schema for the event type emitted. All events that are emitted are given a meta property with the eventType field.

The following example code shows how to send an ecProduct event with the UV API script:

uv.emit('ecProduct', {
  product: {
    id: '112-334-a',
    price: 6.99,
    name: '18th Birthday Baloon',
    category: ['Party Accessories', 'Birthday Parties']
  },
  color: 'red',
  stock: 6,
  eventType: 'detail'
})
// => emits an ecProduct event
Note

Before sending an event to the backend, smartserve.js retrieves context data stored in cookies and meta data such as the URL of the page.

This data will be available to query.
Warning

Any CEH events emitted before the first ecView event are considered invalid. Web and mobile applications emit CEH view events whenever a view is rendered.

The emitted event will have meta attached.

{
  "meta": {
    "type": "ecProduct"
  },
  "product": {
    "id": "112-334-a",
    "price": 6.99,
    "name": "18th Birthday Baloon",
    "category": ["Party Accessories", "Birthday Parties"]
  },
  "color": "red",
  "stock": 6,
  "eventType": "detail"
}

on

uv.on(type, handler, [context])

This method attaches an event handler to be called when a certain event type is emitted. The handler will be passed the event data and will be bound to the context object, if one is passed. If a regex is passed, the handler will execute on events that match the regex.

uv.on('ecProduct', function (data) {
  console.log(data)
})
// => logs data when an `ecProduct` event is emitted

var subscription = uv.on(/.*/, function (data) {
  console.log(data)
})
// => logs data for all events

The on method returns a subscription object which can detach the handler using the dispose method and can also be used to replay events currently in the event array.

Note that subscriptions that have been disposed will not call the handler when replay is called. Let’s look at an example:

subscription.dispose()
// => detatches the event handler

subscription.replay()
// => calls the handler for all events currently in uv.events

once

uv.once(type, handler, [context])

This method attaches an event handler that will be called once, on the next event emitted that matches the type specified. The handler will be passed the event data and will be bound to the context object, if one is passed.

It returns a subscription object which can detach the handler using the dispose method. If a regex is passed, the handler will execute on the next event to match the regex. Let’s look at an example:

uv.once('ecProduct', function (data) {
  console.log(data)
})
emit('ecProduct')
// => logs data

emit('ecProduct')
// => does not log

Events

The events array is a cache of events emitted since the last page load. By iterating over the array it is possible to interpret the user journey or the current state of the page.

NPM module

The uv-api is available on the NPM registry.

npm i uv-api --save

The module exports a createUv function if required using CommonJS.

var createUv = require('uv-api')
var uv = createUv()
uv.emit('ecView')