{"id":4652,"date":"2023-01-04T17:16:41","date_gmt":"2023-01-04T09:16:41","guid":{"rendered":"https:\/\/badgameshow.com\/steven\/?p=4652"},"modified":"2023-01-04T17:16:41","modified_gmt":"2023-01-04T09:16:41","slug":"%e8%a7%a3%e6%b1%bareact-js%e4%b8%ad%e7%9a%84uncaughttypeerrorcannotreadpropertymapofundefined%e9%8c%af%e8%aa%a4","status":"publish","type":"post","link":"https:\/\/badgameshow.com\/steven\/react-js\/%e8%a7%a3%e6%b1%bareact-js%e4%b8%ad%e7%9a%84uncaughttypeerrorcannotreadpropertymapofundefined%e9%8c%af%e8%aa%a4\/","title":{"rendered":"\u89e3\u6c7aReact.js\u4e2d\u7684”UncaughtTypeError:Cannotreadproperty’map’ofundefined”\u932f\u8aa4"},"content":{"rendered":"

<\/p>\n

\u89e3\u6c7a React.js \u4e2d\u7684\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u932f\u8aa4<\/h1>\n

React.js \u662f\u4e00\u500b\u7528\u65bc\u69cb\u5efa\u7528\u6236\u754c\u9762\u7684 JavaScript \u5eab\uff0c\u5b83\u53ef\u4ee5\u8b93\u958b\u767c\u8005\u5feb\u901f\u69cb\u5efa\u529f\u80fd\u5f37\u5927\u7684 Web \u61c9\u7528\u7a0b\u5e8f\u3002\u7136\u800c\uff0c\u5728\u4f7f\u7528 React.js \u6642\uff0c\u958b\u767c\u8005\u53ef\u80fd\u6703\u9047\u5230\u4e00\u4e9b\u554f\u984c\uff0c\u5176\u4e2d\u4e00\u500b\u5e38\u898b\u7684\u932f\u8aa4\u662f\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u3002\u5728\u672c\u6587\u4e2d\uff0c\u6211\u5011\u5c07\u8a73\u7d30\u4ecb\u7d39\u5982\u4f55\u89e3\u6c7a\u9019\u500b\u554f\u984c\u3002<\/p>\n

\u4ec0\u9ebc\u662f\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u932f\u8aa4\uff1f<\/h2>\n

\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u932f\u8aa4\u662f\u4e00\u500b JavaScript \u932f\u8aa4\uff0c\u5b83\u8868\u660e\u4f60\u6b63\u5728\u5617\u8a66\u8a2a\u554f\u4e00\u500b\u672a\u5b9a\u7fa9\u7684\u5c0d\u8c61\u7684\u5c6c\u6027\u3002\u9019\u500b\u932f\u8aa4\u901a\u5e38\u6703\u5728\u4f60\u5617\u8a66\u4f7f\u7528 JavaScript \u7684 map() \u65b9\u6cd5\u6642\u767c\u751f\uff0c\u56e0\u70ba map() \u65b9\u6cd5\u53ea\u80fd\u7528\u65bc\u9663\u5217\u5c0d\u8c61\u3002<\/p>\n

\u5982\u4f55\u89e3\u6c7a\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u932f\u8aa4\uff1f<\/h2>\n

\u8981\u89e3\u6c7a\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u932f\u8aa4\uff0c\u4f60\u9700\u8981\u78ba\u4fdd\u4f60\u6b63\u5728\u4f7f\u7528\u7684\u5c0d\u8c61\u662f\u4e00\u500b\u9663\u5217\u5c0d\u8c61\uff0c\u800c\u4e0d\u662f\u4e00\u500b\u672a\u5b9a\u7fa9\u7684\u5c0d\u8c61\u3002\u4f60\u53ef\u4ee5\u4f7f\u7528 JavaScript \u7684 typeof \u904b\u7b97\u7b26\u4f86\u6aa2\u67e5\u5c0d\u8c61\u7684\u985e\u578b\uff0c\u5982\u679c\u5b83\u4e0d\u662f\u4e00\u500b\u9663\u5217\u5c0d\u8c61\uff0c\u5247\u4f60\u9700\u8981\u5c07\u5b83\u8f49\u63db\u70ba\u9663\u5217\u5c0d\u8c61\u3002<\/p>\n

\n\/\/ \u6aa2\u67e5\u5c0d\u8c61\u7684\u985e\u578b\nif (typeof myObject !== 'object') {\n  \/\/ \u5c07\u5c0d\u8c61\u8f49\u63db\u70ba\u9663\u5217\u5c0d\u8c61\n  myObject = [myObject];\n}\n\n\/\/ \u4f7f\u7528 map() \u65b9\u6cd5\nmyObject.map(function(item) {\n  \/\/ \u5c0d\u9663\u5217\u4e2d\u7684\u6bcf\u500b\u5143\u7d20\u57f7\u884c\u64cd\u4f5c\n});\n<\/pre>\n
\u53e6\u5916\uff0c\u4f60\u4e5f\u53ef\u4ee5\u4f7f\u7528 JavaScript \u7684 Array.isArray() \u65b9\u6cd5\u4f86\u6aa2\u67e5\u5c0d\u8c61\u662f\u5426\u70ba\u9663\u5217\u5c0d\u8c61\uff0c\u5982\u679c\u4e0d\u662f\uff0c\u5247\u4f60\u53ef\u4ee5\u5c07\u5b83\u8f49\u63db\u70ba\u9663\u5217\u5c0d\u8c61\uff1a<\/p>\n
\n\/\/ \u6aa2\u67e5\u5c0d\u8c61\u662f\u5426\u70ba\u9663\u5217\u5c0d\u8c61\nif (!Array.isArray(myObject)) {\n  \/\/ \u5c07\u5c0d\u8c61\u8f49\u63db\u70ba\u9663\u5217\u5c0d\u8c61\n  myObject = [myObject];\n}\n\n\/\/ \u4f7f\u7528 map() \u65b9\u6cd5\nmyObject.map(function(item) {\n  \/\/ \u5c0d\u9663\u5217\u4e2d\u7684\u6bcf\u500b\u5143\u7d20\u57f7\u884c\u64cd\u4f5c\n});\n<\/pre>\n
\u5982\u679c\u4f60\u6b63\u5728\u4f7f\u7528 React.js\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528 React.Children.map() \u65b9\u6cd5\u4f86\u8655\u7406\u672a\u5b9a\u7fa9\u7684\u5c0d\u8c61\uff1a<\/p>\n
\nReact.Children.map(myObject, function(item) {\n  \/\/ \u5c0d\u9663\u5217\u4e2d\u7684\u6bcf\u500b\u5143\u7d20\u57f7\u884c\u64cd\u4f5c\n});\n<\/pre>\n
\u7e3d\u7d50<\/h2>\n
\u5728\u672c\u6587\u4e2d\uff0c\u6211\u5011\u8a73\u7d30\u4ecb\u7d39\u4e86\u5982\u4f55\u89e3\u6c7a React.js \u4e2d\u7684\u300cUncaught TypeError: Cannot read property ‘map’ of undefined\u300d\u932f\u8aa4\u3002\u9996\u5148\uff0c\u4f60\u9700\u8981\u78ba\u4fdd\u4f60\u6b63\u5728\u4f7f\u7528\u7684\u5c0d\u8c61\u662f\u4e00\u500b\u9663\u5217\u5c0d\u8c61\uff0c\u800c\u4e0d\u662f\u4e00\u500b\u672a\u5b9a\u7fa9\u7684\u5c0d\u8c61\u3002\u4f60\u53ef\u4ee5\u4f7f\u7528 JavaScript \u7684 typeof \u904b\u7b97\u7b26\u6216 Array.isArray() \u65b9\u6cd5\u4f86\u6aa2\u67e5\u5c0d\u8c61\u7684\u985e\u578b\uff0c\u5982\u679c\u5b83\u4e0d\u662f\u4e00\u500b\u9663\u5217\u5c0d\u8c61\uff0c\u5247\u4f60\u9700\u8981\u5c07\u5b83\u8f49\u63db\u70ba\u9663\u5217\u5c0d\u8c61\u3002\u5982\u679c\u4f60\u6b63\u5728\u4f7f\u7528 React.js\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528 React.Children.map() \u65b9\u6cd5\u4f86\u8655\u7406\u672a\u5b9a\u7fa9\u7684\u5c0d\u8c61\u3002<\/p>\n
<\/p>\n
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\u6587\u7ae0\u6458\u8981\uff1a\u672c\u6587\u5c07\u4ecb\u7d39\u5982\u4f55\u89e3\u6c7aReact.js\u4e2d\u7684”UncaughtTypeError:Cannotreadproperty’map’ofundefined”\u932f\u8aa4\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u6709\u7528\u7684\u6280\u5de7\uff0c\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u89e3\u6c7a\u6b64\u985e\u554f\u984c\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":[184,183],"tags":[182,181],"class_list":["post-4652","post","type-post","status-publish","format-standard","hentry","category-react","category-react-js","tag-react","tag-react-js"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack-related-posts":[],"jetpack_shortlink":"https:\/\/wp.me\/pcFK27-1d2","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts\/4652","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=4652"}],"version-history":[{"count":1,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts\/4652\/revisions"}],"predecessor-version":[{"id":4653,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/posts\/4652\/revisions\/4653"}],"wp:attachment":[{"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/media?parent=4652"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/categories?post=4652"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/badgameshow.com\/steven\/wp-json\/wp\/v2\/tags?post=4652"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}