[feature] Support line feed char "\n" in the "formatter function".

src/util/toString.js

@@ -1,7 +1,8 @@
 export default function toString(obj) {
   let result = JSON.stringify(obj, function (key, val) {
     if (typeof val === "function") {
-      return `~--demo--~${val}~--demo--~`;
+      // This "replace function" is used to remove the useless line feeds among code.
+      return `~--demo--~${val}~--demo--~`.replace(/\n/g, '');
     }
     return val;
   });
@@ -10,7 +11,7 @@ export default function toString(obj) {
     result = result
       .replace('"~--demo--~', "")
       .replace('~--demo--~"', "")
-      .replace(/\\n/g, "")
+      .replace(/\\\\/g, '\\') // When the formatter function convert to string, '\n' in the return string will be replaced by '\\n', this "replace function" will replace it back to line feed '\n'.
       .replace(/\\\"/g, '"'); //最后一个replace将release模式中莫名生成的\"转换成"
   } while (result.indexOf("~--demo--~") >= 0);
   // 添加此行把unicode转为中文（否则formatter函数中含有中文在release版本中显示不出来）