Add language.js

book.toml

@@ -6,5 +6,5 @@ language = "zh-CN"
 
 [output.html]
 additional-css = ["ferris.css", "theme/2018-edition.css"]
-additional-js = ["ferris.js"]
+additional-js = ["ferris.js", "language.js"]
 git-repository-url = "https://github.com/rust-lang-cn/book-cn"

language.js

@@ -0,0 +1,33 @@
+(function () {
+  var url = window.location.href;
+  var host = window.location.host;
+
+  var search = {
+    en: "/en/",
+    zh_CN: "/zh-CN/"
+  }
+
+  var replaceWith = {
+    en: "/zh-CN/",
+    zh_CN: "/en/"
+  }
+
+
+  var link = "";
+  var word = "";
+
+  if (url.indexOf(search.en) != -1 && url.indexOf(search.en) === (url.indexOf(host) + host.length)) {
+    link = url.replace(search.en, replaceWith.en);
+    word = "简体中文";
+  } else if (url.indexOf(search.zh_CN) != -1 && url.indexOf(search.zh_CN) === (url.indexOf(host) + host.length)) {
+    link = url.replace(search.zh_CN, replaceWith.zh_CN);
+    word = "English";
+  }
+
+  var node = '<a href="' + link + '"><i id="print-button" class="fa fa-language"> ' + word + '</i></a>';
+  var insertNode = document.getElementsByClassName('right-buttons');
+  if (insertNode.length > 0 && link != "") {
+    var html = insertNode[0].innerHTML;
+    insertNode[0].innerHTML = html + node;
+  }
+})()