# Advanced

The following are tips for advanced use cases.

# Override Properties

You may explicitly set or override properties and have then be recalled even in subsequent user visits where the original or full context may not be available.

// Examples: bta('set{PropertyName}')

// Sets UserId. If property is not defined in subsequent
// data, it will still be populated from the previous value
// Note: getRequest() is just a placeholder function that 
// returns the data like: 
// return { currency: "USD", value: 1234.56}
bta('setUserId', "mynewuserid");
bta('download', {...getRequest(), userId: undefined});

# Send Data for Multiple Keys

You may send data to multiple keys.

// multiple keys
bta('registerKey', '{{ KEY_1 }}');
bta('registerKey', '{{ KEY_2 }}');
bta('registerKey', '{{ KEY_3 }}');
bta('registerKey', '{{ KEY_1 }}');
// remove 'KEY 1' from receiving data
bta('unregisterKey', '{{ KEY_1 }}');
// will send data to both 'KEY_2' and 'KEY_3'
bta('lead', getRequest());

// send data only for 'KEY_1'
bta('viewitem', getRequest(), '{{ KEY_1 }}')
// send data event only for 'KEY_2'
bta('viewitem', getRequest(), '{{ KEY_2 }}')

# Selective Data for Multiple Keys

You may send different data to different keys.

// send one event only for 'KEY_1'
bta('viewitem', getRequest1(), '{{ KEY_1 }}')
// send one event only for 'KEY_2'
bta('viewitem', getRequest2(), '{{ KEY_2 }}')
// send one event with the intial config key from 
// the install/page load
bta('viewitem', getRequest1())

# Callbacks

If you need to run code after the data is sent, you may execute callbacks.

// Run callback/execute code on success
function withcallbacksuccess() {
  window['onBacktracksAttributionSuccess'] = function (result) {
    console.log('Success:', result);
    window['onBacktracksAttributionSuccess'] = undefined;

    // ...

// Run callback/execute code on failure
function withcallbackfailure() {
  window['onBacktracksAttributionFailure'] = function (result) {
    console.log('Failure:', result);
    window['onBacktracksAttributionFailure'] = undefined;

    // ...

# Delay Event Fires

If you want to delay the recording of events to do something like only track data for engaged visitors or after N seconds on a page you can accomplish this by adding a delay with setTimeout.

// Delay by N seconds
var seconds = 5;
setTimeout(function() {
    // ...
}, seconds * 1000);

# Install Using IMG Tag

In cases where you cannot execute JavaScript, you may install and run the Backtracks Attribution tracker with a HTML <img> tag.

<img src="https://api.backtracks.fm/v1/attribution/image?k=YOUR_BT_KEY
  height="1" width="1" style="display:none"/>

To fire a purchase event for example, you may construct an event similar to the following, while passing in any custom parameters that are applicable to your scenario.

<img height="1" width="1" style="display:none" 
 src="https://api.backtracks.fm/v1/attribution/image?k=abc123&e=purchase&d[currency]=USD&d[value]=123.45&d[tax]=1.23&d[shipping]=1.24&d[transactionId]=67ebba62-5534-4048-b74a-9e6ff15bd90a" />

If the <img> tag is loaded within an iframe that is sandboxed with the sandbox attribute, then allow-scripts property must be added to the iframe.

<iframe src="https://example.com/example-iframe-with-img-tag" sandbox="allow-scripts"></iframe>

# Content Security Policy

If your website has implemented a Content Security Policy, allow JavaScript to load from https://c.backtracks.fm and/or *.backtracks.fm.