gatsby-browser.js有什么作用？

  // gatsby-browser.js
  const React = require("react")
  // Logs when the client route changes
  exports.onRouteUpdate = ({ location, prevLocation }) => {

console.log("new pathname", location.pathname)

console.log("old pathname", prevLocation ? prevLocation.pathname : null)

  }

 // gatsby-browser.js
  const React = require("react")
  const Layout = require("./src/components/layout")
  // Wraps every page in a component
  exports.wrapPageElement = ({ element, props }) => {

return <Layout {...props}>{element}</Layout>

  }