{"id":4830,"date":"2023-01-05T10:39:47","date_gmt":"2023-01-05T02:39:47","guid":{"rendered":"https:\/\/badgameshow.com\/steven\/?p=4830"},"modified":"2023-01-05T10:39:47","modified_gmt":"2023-01-05T02:39:47","slug":"%e4%ba%86%e8%a7%a3typescript%e7%b1%bb%e5%9e%8b%e8%b0%93%e8%af%8d%e7%9a%84%e5%8a%9f%e8%83%bd%e8%88%87%e5%84%aa%e5%8b%a2","status":"publish","type":"post","link":"https:\/\/badgameshow.com\/steven\/typescript\/%e4%ba%86%e8%a7%a3typescript%e7%b1%bb%e5%9e%8b%e8%b0%93%e8%af%8d%e7%9a%84%e5%8a%9f%e8%83%bd%e8%88%87%e5%84%aa%e5%8b%a2\/","title":{"rendered":"\u4e86\u89e3TypeScript\u7c7b\u578b\u8c13\u8bcd\u7684\u529f\u80fd\u8207\u512a\u52e2"},"content":{"rendered":"

<\/p>\n

\u4ec0\u9ebc\u662f TypeScript \u7c7b\u578b\u8c13\u8bcd\uff1f<\/h1>\n

TypeScript \u7c7b\u578b\u8c13\u8bcd\uff08type predicate\uff09\u662f\u4e00\u7a2e\u7528\u65bc\u6aa2\u67e5\u985e\u578b\u7684\u8a9e\u6cd5\uff0c\u5b83\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u8b8a\u91cf\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\uff0c\u6216\u8005\u6aa2\u67e5\u4e00\u500b\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\u3002\u5b83\u53ef\u4ee5\u8b93\u958b\u767c\u8005\u66f4\u5bb9\u6613\u5730\u6aa2\u67e5\u548c\u64cd\u4f5c\u8b8a\u91cf\uff0c\u4e26\u4e14\u53ef\u4ee5\u6e1b\u5c11\u7a0b\u5f0f\u78bc\u4e2d\u7684\u932f\u8aa4\u3002<\/p>\n

TypeScript \u7c7b\u578b\u8c13\u8bcd\u7684\u8a9e\u6cd5\u662f x is T<\/code>\uff0c\u5176\u4e2d x<\/code> \u662f\u4e00\u500b\u8b8a\u91cf\uff0c\u800c T<\/code> \u662f\u4e00\u500b\u985e\u578b\u3002\u5982\u679c x<\/code> \u7684\u985e\u578b\u662f T<\/code>\uff0c\u5247\u8868\u9054\u5f0f\u7684\u503c\u70ba true<\/code>\uff0c\u5426\u5247\u70ba false<\/code>\u3002<\/p>\n

\u4f7f\u7528 TypeScript \u7c7b\u578b\u8c13\u8bcd<\/h2>\n

TypeScript \u7c7b\u578b\u8c13\u8bcd\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u8b8a\u91cf\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\uff0c\u4ee5\u53ca\u6aa2\u67e5\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\u3002<\/p>\n

\u6aa2\u67e5\u8b8a\u91cf\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b<\/h3>\n

\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u8b8a\u91cf x<\/code>\uff0c\u5b83\u7684\u985e\u578b\u53ef\u80fd\u662f string<\/code> \u6216 number<\/code>\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528 TypeScript \u7c7b\u578b\u8c13\u8bcd\u4f86\u6aa2\u67e5\u5b83\u7684\u985e\u578b\uff1a<\/p>\n

let x: string | number;\n\nif (x is string) {\n  \/\/ x \u662f string\n} else if (x is number) {\n  \/\/ x \u662f number\n}\n<\/code><\/pre>\n
\u6aa2\u67e5\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b<\/h3>\n
\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u51fd\u6578 foo<\/code>\uff0c\u5b83\u7684\u53c3\u6578 x<\/code> \u7684\u985e\u578b\u53ef\u80fd\u662f string<\/code> \u6216 number<\/code>\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528 TypeScript \u7c7b\u578b\u8c13\u8bcd\u4f86\u6aa2\u67e5\u5b83\u7684\u985e\u578b\uff1a<\/p>\n
function foo(x: string | number) {\n  if (x is string) {\n    \/\/ x \u662f string\n  } else if (x is number) {\n    \/\/ x \u662f number\n  }\n}\n<\/code><\/pre>\n
\u7e3d\u7d50<\/h2>\n
TypeScript \u7c7b\u578b\u8c13\u8bcd\u662f\u4e00\u7a2e\u7528\u65bc\u6aa2\u67e5\u985e\u578b\u7684\u8a9e\u6cd5\uff0c\u5b83\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u8b8a\u91cf\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\uff0c\u6216\u8005\u6aa2\u67e5\u4e00\u500b\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\u3002\u5b83\u53ef\u4ee5\u8b93\u958b\u767c\u8005\u66f4\u5bb9\u6613\u5730\u6aa2\u67e5\u548c\u64cd\u4f5c\u8b8a\u91cf\uff0c\u4e26\u4e14\u53ef\u4ee5\u6e1b\u5c11\u7a0b\u5f0f\u78bc\u4e2d\u7684\u932f\u8aa4\u3002TypeScript \u7c7b\u578b\u8c13\u8bcd\u7684\u8a9e\u6cd5\u662f x is T<\/code>\uff0c\u5176\u4e2d x<\/code> \u662f\u4e00\u500b\u8b8a\u91cf\uff0c\u800c T<\/code> \u662f\u4e00\u500b\u985e\u578b\u3002\u5982\u679c x<\/code> \u7684\u985e\u578b\u662f T<\/code>\uff0c\u5247\u8868\u9054\u5f0f\u7684\u503c\u70ba true<\/code>\uff0c\u5426\u5247\u70ba false<\/code>\u3002TypeScript \u7c7b\u578b\u8c13\u8bcd\u53ef\u4ee5\u7528\u65bc\u6aa2\u67e5\u8b8a\u91cf\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\uff0c\u4ee5\u53ca\u6aa2\u67e5\u51fd\u6578\u7684\u53c3\u6578\u662f\u5426\u70ba\u67d0\u500b\u985e\u578b\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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