import { inBrowser } from './env'

export let mark

export let measure

if (process.env.NODE_ENV !== 'production') {
  //如果在浏览器环境,

  const perf = inBrowser &&window.performance  /* istanbul ignore if */

  if (

    perf &&

    perf.mark &&

    perf.measure &&

    perf.clearMarks &&

    perf.clearMeasures

  ) {

    mark = tag => perf.mark(tag)

    measure= (name, startTag, endTag) => {

      perf.measure(name, startTag, endTag)

      perf.clearMarks(startTag)

      perf.clearMarks(endTag)

      perf.clearMeasures(name)

    }

  }

}