React计算器项目无法通过freeCodeCamp测试：八进制字面量严格模式错误

我为freeCodeCamp课程制作了一个React计算器作为期末项目，自认为满足所有要求，但无法通过测试。测试显示如下错误：

Uncaught SyntaxError: Octal literals are not allowed in strict mode. (http: //127.0.0.1:3000/:1)
Error: Uncaught SyntaxError: Octal literals are not allowed in strict mode. (http: //127.0.0.1:3000/:1)
at r.onerror (https://cdn.freecodecamp.org/testable-projects-fcc/vl/bundle.js:575:14032)
at Object. invokeGuardedCallbackDev (static/is/bundle.js: 12074:20)
at invokeGuardedCallback (static/is/bundle. js:12136:35)
at invokeGuardedCallbackAndCatchFirstError (static/is/bundle. is: 12151:29)
at executeDispatch (static/js/bundle.js: 16980:7)
at processDispatchQueueItemsInOrder(static/js/bundle.js:17012:11)
at processDispatchQueue (static/js/bundle. js:17025:9)
at dispatchEventsForPlugins (static/is/bundle. js:17036:7)
at http://127.0.0.1:3000/static/is/bundle.is:17228:16
at batchedUpdates$1 (static/js/bundle.js: 33863:16)

我是编程新手，希望得到帮助或提示以找出错误位置及修复方法。若需调试可通过npm start启动项目，GitHub仓库地址：https://github.com/JiriAU/calculator_react_v1

内容的提问来源于stack exchange，提问作者JiriAU