webpack reference erro window.location.hostname cannot be found, vue.js

Question

Any help would be really appreciated on this issue.

I want to set the proxy target dynamically inside webpack index.js

proxyTable: {
    '/api': {
    target: 'http://' +  window.location.hostname.split('.')[0] + '.example.com',
    changeOrigin: true,
    pathRewrite: {
      '^/api': ''
    }
  }
},

and webpack is giving error ReferenceError: window is not defined