How to use the @nuxt/utils.isUrl function in @nuxt/utils

// If app.html is defined, set the template path to the user template
  if (options.appTemplatePath === undefined) {
    options.appTemplatePath = path.resolve(options.buildDir, 'views/app.template.html')
    if (fs.existsSync(path.join(options.srcDir, 'app.html'))) {
      options.appTemplatePath = path.join(options.srcDir, 'app.html')
    }
  } else {
    options.appTemplatePath = path.resolve(options.srcDir, options.appTemplatePath)
  }

  options.build.publicPath = options.build.publicPath.replace(/([^/])$/, '$1/')
  options.build._publicPath = options.build._publicPath.replace(/([^/])$/, '$1/')

  // Ignore publicPath on dev
  if (options.dev && isUrl(options.build.publicPath)) {
    options.build.publicPath = options.build._publicPath
  }

  // If store defined, update store options to true unless explicitly disabled
  if (
    options.store !== false &&
    fs.existsSync(path.join(options.srcDir, options.dir.store)) &&
    fs.readdirSync(path.join(options.srcDir, options.dir.store))
      .find(filename => filename !== 'README.md' && filename[0] !== '.')
  ) {
    options.store = true
  }

  // SPA loadingIndicator
  if (options.loadingIndicator) {
    // Normalize loadingIndicator

constructor (nuxt) {
    this.nuxt = nuxt
    this.options = nuxt.options

    this.globals = determineGlobals(nuxt.options.globalName, nuxt.options.globals)

    this.publicPath = isUrl(this.options.build.publicPath)
      ? this.options.build._publicPath
      : this.options.build.publicPath

    // Runtime shared resources
    this.resources = {}

    // Will be set after listen
    this.listeners = []

    // Create new connect instance
    this.app = connect()

    // Close hook
    this.nuxt.hook('close', () => this.close())

    // devMiddleware placeholder

constructor (nuxt, builder) {
    this.nuxt = nuxt
    this.options = nuxt.options
    this.builder = builder

    // Set variables
    this.staticRoutes = path.resolve(this.options.srcDir, this.options.dir.static)
    this.srcBuiltPath = path.resolve(this.options.buildDir, 'dist', 'client')
    this.distPath = this.options.generate.dir
    this.distNuxtPath = path.join(
      this.distPath,
      isUrl(this.options.build.publicPath) ? '' : this.options.build.publicPath
    )
  }