perf.js

import config from '../config'
import { inBrowser } from './env'

export let mark
export let measure

if (process.env.NODE_ENV !== 'production') {
  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)
      if (!config.performance) {
        perf.clearMarks(startTag)
        perf.clearMarks(endTag)
        perf.clearMeasures(name)
      }
    }
  }
}