javascriptangularjsangular-ui-router

What does the {lang:(?:da|en)} do in Javascript?

I am trying to understand what this state means in ui-router:

$stateProvider.state('app', {
  abstract: true,
  url: '/{lang:(?:da|en)}',
  template: '<ui-view/>'
});
$stateProvider.state('app.home', {
  url: '',
    templateUrl: 'views/home-page.html',
});

Specifically what does {lang:(?:da|en)} do. I've not seen this construct before.

Solution

  • This is using what is called Regex Parameters You can see their documentation here

    So, /{lang:(?:da|en)} means to check that the lang parameter is either da or en. If so, then render the template.

    Specifically, this will match /da, or /en