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Tracking custom event properties for auto-tracked events

If you are using one of our prebuilt source integrations, and you want to include custom properties (or modify existing properties) on these events; then you can do so using the set method. Imagine for example that I want to send a custom property with my Added To Cart event. I would then call the following function before the Added To Cart event is fired. 
cvg({method: "set", eventProperties: {hello:"world"}})
When my Added To Cart event fires, it will now include the custom hello -> world property mapping. You can modify profile properties in the same way, a full example of the function would be: 
cvg({method: "set", properties: {...profileProperties}, eventProperties: {...eventProperties}})