beforeSend (Data Interception and Data Modification)¶

RUM SDK executes the beforeSend method before each data is sent, and by customizing the implementation of this method, the following operations can be performed:

• Modify some data
• Intercept data transmission

beforeSend provides two parameters:

function beforeSend(event, context)

event is an object generated by the SDK that collects various metrics data. context refers to specific relevant information as follows:

Modify Some Data¶

window.DATAFLUX_RUM &&
    window.DATAFLUX_RUM.init({
        ...,
        beforeSend: (event, context) => {
            if (event.type === 'resource' && event.resource.type === 'fetch') {
                // Add response headers information to the original data
                event.context = {...event.context, responseHeaders: context.response.headers}
            }
        },
        ...
    });

The fields that the SDK allows to be modified are listed in the table below:

Intercept Data Transmission¶

You can intercept unnecessary data by returning true or false through the beforeSend method.

• true means this data needs to be reported
• false means this data should be ignored

window.DATAFLUX_RUM &&
    window.DATAFLUX_RUM.init({
        ...,
        beforeSend: (event) => {
            if (shouldDiscard(event)) {
                return false
            } else {
                return true
            }
            ...
        },
        ...
    });