Uncaught ReferenceError: exports is not defined

使用的是Vue-cli创建的项目，我写了一个js文件，里面有一些会用到的函数。但这里突然就不能用了，找不出什么毛病啊。

import ol from 'openlayers'

const isLayerExist = (id) => {
  let isExist = false
  window.map.getLayers().forEach(function (layer) {
    if (layer.get('id') === id) {
      isExist = true
    }
  })
  return isExist
}

const toggleLayerVisible = (id, show) => {
  window.map.getLayers().forEach(function (layer) {
    if (layer.get('id') === id) {
      layer.setVisible(show)
    }
  })
}

const generateLayer = ({type, url, id}) => {
  switch (type) {
    case 'ImageWMS':
      createImageWMS({url, id})
      break
    default:
      break
  }
}

const createImageWMS = (url, id, opacity = 0.9) => {
  let tiled = new ol.layer.Image({
    opacity: opacity,
    source: new ol.source.ImageWMS({
      url: url,
      wrapX: false
    }),
    visible: true,
    id: id
  })
  window.map.addLayer(tiled)
}

exports.isLayerExist = isLayerExist
exports.toggleLayerVisible = toggleLayerVisible
exports.generateLayer = generateLayer

在组件里面是这样引用的 import maputils from '../utils/maputils'

vue界面就出不来了，引用其他文件是可以的，到这儿就行了，程序界面直接无法访问。命令行里面也没有报错，而浏览器里面说是

Uncaught ReferenceError: exports is not defined