Internal approach

Opa now provides support for translation by means of the @i18n directive. We can put a translation function inside the @i18n directive, and it will be replaced by a proper value according to different languages. An example is worth a thousand words, so let's get started with a simple example:

import stdlib.web.client
hello = function {
  case "en": "Hello"
  case "fr": "Bonjour"
  case "zh": "你好"
  default: "Hi"
}
function page(){
  <h1> {@i18n(hello)} </h1>
  <input type="button" value="English" onclick={set_lang("en")}/>
  <input type="button" value="French"  onclick={set_lang("fr")}/>
  <input type="button" value="Chinese" onclick={set_lang("zh")}/>
}
function set_lang(lang)(_){
  I18n.set_lang(lang)
  Client.reload()
}
Server.start(Server.http, {title:"Opa Packt", ~page})

Save this code into a file, 801.opa, then compile and run it with the following command:

opa 801.opa --

The result looks as shown in the following screenshot:

The page shows...