beforeSend (Data Interception and Data Modification)¶

The RUM SDK executes the beforeSend method before sending each piece of data. By customizing the implementation of this method, you can achieve the following operations:

• Modify certain data;
• Intercept data transmission.

beforeSend provides two parameters:

function beforeSend(event, context)

Modify Certain 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}
            }
        },
        ...
    });

Note: beforeSend can only modify data fields that the SDK allows. Modifications outside these fields will be ignored.

The fields that the SDK allows modification are listed in the table below:

Intercept Data Transmission¶

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

• true means this data should 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
            }
            ...
        },
        ...
    });