function handleTriggerHeader(xhr, header, elt) {
    const triggerBody = xhr.getResponseHeader(header)
    if (triggerBody.indexOf('{') === 0) {
      const triggers = parseJSON(triggerBody)
      for (const eventName in triggers) {
        if (triggers.hasOwnProperty(eventName)) {
          let detail = triggers[eventName]
          if (isRawObject(detail)) {
            // @ts-ignore
            elt = detail.target !== undefined ? detail.target : elt
          } else {
            detail = { value: detail }
          }
          triggerEvent(elt, eventName, detail)
        }
      }
    } else {
      const eventNames = triggerBody.split(',')
      for (let i = 0; i < eventNames.length; i++) {
        triggerEvent(elt, eventNames[i].trim(), [])
      }
    }
  }
@param {XMLHttpRequest} xhr
@param {string} header
@param {EventTarget} elt