{"id":5344,"date":"2023-01-05T12:29:54","date_gmt":"2023-01-05T04:29:54","guid":{"rendered":"https:\/\/badgameshow.com\/steven\/?p=5344"},"modified":"2023-01-05T12:29:54","modified_gmt":"2023-01-05T04:29:54","slug":"%e4%ba%86%e8%a7%a3typescript%e4%b8%ad%e7%9a%84undefined%e5%8a%9f%e8%83%bd","status":"publish","type":"post","link":"https:\/\/badgameshow.com\/steven\/typescript\/%e4%ba%86%e8%a7%a3typescript%e4%b8%ad%e7%9a%84undefined%e5%8a%9f%e8%83%bd\/","title":{"rendered":"\u4e86\u89e3TypeScript\u4e2d\u7684undefined\u529f\u80fd"},"content":{"rendered":"

<\/p>\n

TypeScript \u4e2d\u7684 undefined<\/h1>\n

TypeScript \u662f\u4e00\u7a2e JavaScript \u7684\u8d85\u96c6\uff0c\u5b83\u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u529f\u80fd\uff0c\u4f8b\u5982\u985e\u578b\u6aa2\u67e5\u548c\u7de8\u8b6f\u5668\u3002\u5728 TypeScript \u4e2d\uff0cundefined \u662f\u4e00\u500b\u7279\u6b8a\u7684\u503c\uff0c\u5b83\u8868\u793a\u4e00\u500b\u672a\u5b9a\u7fa9\u7684\u503c\u3002<\/p>\n

\u5728 JavaScript \u4e2d\uff0cundefined \u662f\u4e00\u500b\u5168\u5c40\u8b8a\u91cf\uff0c\u5b83\u8868\u793a\u4e00\u500b\u672a\u5b9a\u7fa9\u7684\u503c\u3002\u5728 TypeScript \u4e2d\uff0cundefined \u4e5f\u662f\u4e00\u500b\u5168\u5c40\u8b8a\u91cf\uff0c\u4f46\u5b83\u662f\u4e00\u500b\u7279\u6b8a\u7684\u503c\uff0c\u5b83\u53ef\u4ee5\u7528\u4f86\u8868\u793a\u4e00\u500b\u672a\u5b9a\u7fa9\u7684\u503c\u3002<\/p>\n

\u5728 TypeScript \u4e2d\uff0cundefined \u53ef\u4ee5\u7528\u4f86\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u662f\u5426\u5df2\u7d93\u88ab\u5b9a\u7fa9\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u662f\u5426\u5df2\u7d93\u88ab\u5b9a\u7fa9\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u4ee3\u78bc\uff1a<\/p>\n

\nif (typeof myVariable === \"undefined\") {\n    \/\/ myVariable is not defined\n}\n<\/pre>\n
\u5728 TypeScript \u4e2d\uff0cundefined \u4e5f\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u662f\u5426\u70ba null\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u662f\u5426\u70ba null\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u4ee3\u78bc\uff1a<\/p>\n
\nif (myVariable === null || typeof myVariable === \"undefined\") {\n    \/\/ myVariable is null or undefined\n}\n<\/pre>\n
\u5728 TypeScript \u4e2d\uff0cundefined \u4e5f\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u4e00\u500b\u51fd\u6578\u662f\u5426\u6709\u8fd4\u56de\u503c\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u6aa2\u67e5\u4e00\u500b\u51fd\u6578\u662f\u5426\u6709\u8fd4\u56de\u503c\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u4ee3\u78bc\uff1a<\/p>\n
\nif (typeof myFunction() === \"undefined\") {\n    \/\/ myFunction does not return a value\n}\n<\/pre>\n
\u5728 TypeScript \u4e2d\uff0cundefined \u4e5f\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u4e00\u500b\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u6709\u503c\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u6aa2\u67e5\u4e00\u500b\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u6709\u503c\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u4ee3\u78bc\uff1a<\/p>\n
\nif (typeof myFunction(myParameter) === \"undefined\") {\n    \/\/ myParameter is not defined\n}\n<\/pre>\n
\u7e3d\u4e4b\uff0c\u5728 TypeScript \u4e2d\uff0cundefined \u662f\u4e00\u500b\u7279\u6b8a\u7684\u503c\uff0c\u5b83\u53ef\u4ee5\u7528\u4f86\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u3001\u51fd\u6578\u6216\u53c3\u6578\u662f\u5426\u6709\u503c\u3002<\/p>\n
<\/p>\n
TypeScript \u4e2d\u7684 undefined \u7684\u512a\u9ede<\/h2>\n
TypeScript \u4e2d\u7684 undefined \u6709\u8a31\u591a\u512a\u9ede\uff0c\u4f8b\u5982\uff1a<\/p>\n
    \n
  • \u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u5b89\u5168\u6027\uff1a<\/strong>TypeScript \u4e2d\u7684 undefined \u53ef\u4ee5\u7528\u4f86\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u3001\u51fd\u6578\u6216\u53c3\u6578\u662f\u5426\u6709\u503c\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u7a0b\u5f0f\u78bc\u4e2d\u7684\u932f\u8aa4\u3002<\/li>\n
  • \u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u53ef\u8b80\u6027\uff1a<\/strong>TypeScript \u4e2d\u7684 undefined \u53ef\u4ee5\u8b93\u7a0b\u5f0f\u78bc\u66f4\u5bb9\u6613\u95b1\u8b80\uff0c\u56e0\u70ba\u5b83\u53ef\u4ee5\u6e05\u695a\u5730\u8868\u660e\u4e00\u500b\u8b8a\u91cf\u3001\u51fd\u6578\u6216\u53c3\u6578\u662f\u5426\u6709\u503c\u3002<\/li>\n
  • \u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u53ef\u7dad\u8b77\u6027\uff1a<\/strong>TypeScript \u4e2d\u7684 undefined \u53ef\u4ee5\u8b93\u7a0b\u5f0f\u78bc\u66f4\u5bb9\u6613\u7dad\u8b77\uff0c\u56e0\u70ba\u5b83\u53ef\u4ee5\u6e05\u695a\u5730\u8868\u660e\u4e00\u500b\u8b8a\u91cf\u3001\u51fd\u6578\u6216\u53c3\u6578\u662f\u5426\u6709\u503c\u3002<\/li>\n<\/ul>\n
    \u7e3d\u7d50<\/h2>\n
    \u7e3d\u4e4b\uff0cTypeScript \u4e2d\u7684 undefined \u662f\u4e00\u500b\u7279\u6b8a\u7684\u503c\uff0c\u5b83\u53ef\u4ee5\u7528\u4f86\u6aa2\u67e5\u4e00\u500b\u8b8a\u91cf\u3001\u51fd\u6578\u6216\u53c3\u6578\u662f\u5426\u6709\u503c\u3002\u5b83\u6709\u8a31\u591a\u512a\u9ede\uff0c\u4f8b\u5982\u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u5b89\u5168\u6027\u3001\u53ef\u8b80\u6027\u548c\u53ef\u7dad\u8b77\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
    \u672c\u6587\u5c07\u4ecb\u7d39TypeScript\u4e2d\u7684undefined\u529f\u80fd\uff0c\u8a73\u7d30\u89e3\u91cbundefined\u7684\u5b9a\u7fa9\u3001\u4f7f\u7528\u65b9\u6cd5\u3001\u548c\u5b83\u8207null\u7684\u5340\u5225\uff0c\u8b93\u4f60\u66f4\u52a0\u4e86\u89e3TypeScript\u4e2d\u7684undefined\u529f\u80fd\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[187],"tags":[186],"class_list":["post-5344","post","type-post","status-publish","format-standard","hentry","category-typescript","tag-typescript"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack-related-posts":[],"jetpack_shortlink":"https:\/\/wp.me\/pcFK27-1oc","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts\/5344","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/comments?post=5344"}],"version-history":[{"count":1,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts\/5344\/revisions"}],"predecessor-version":[{"id":5345,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts\/5344\/revisions\/5345"}],"wp:attachment":[{"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/media?parent=5344"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/categories?post=5344"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/tags?post=5344"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}