\u53ea\u662f\u5b66\u4e60\u7b14\u8bb0\u3002<\/p>\n
<\/p>\n
\u9047\u5230\u590d\u6742\u7684\u7c7b\u578b\u5b9a\u4e49\uff0c\u5c31\u5f97\u7528TypeScript \u4e2d\u7684\u6cdb\u578b\u4e86\u3002<\/p>\n
\u5176\u5b9e\u6cdb\u578b\u53ef\u4ee5\u8bf4\u662f\u7c7b\u578b\u7684\u53d8\u91cf\u3002\u4ece\u6700\u7b80\u5355\u7684\u4f8b\u5b50\u770b\u8d77<\/p>\n
function identity<T>(arg: T): T {\n return arg;\n}<\/pre>\n\u8fd9\u4e2a\u51fd\u6570\u53ea\u662f\u60f3\u8868\u8fbe\u4e00\u4e0b\uff0c\u8f93\u5165\u5565\u7c7b\u578b\u5c31\u8fd4\u56de\u5565\u7c7b\u578b\u3002\u7136\u800c\u8f93\u5165\u7c7b\u578b\u53ef\u80fd\u6709\u5f88\u591a\u79cd\uff0c\u8fd9\u65f6\u5019\u5c31\u9700\u8981\u4e00\u4e2a\u6cdb\u578b\uff0cT\u662f\u4e00\u4e2a\u7c7b\u578b\u7684\u53d8\u91cf\u3002<\/p>\n
function identity<T>(arg: T[]): T {\n return arg[1];\n}<\/pre>\n\u8fd9\u4e2a\u53ef\u4ee5\u66f4\u76f4\u89c2\u770b\u51faT\u662f\u4e2a\u7c7b\u578b\u7684\u53d8\u91cf\uff0c\u8f93\u5165T\u7c7b\u578b\u7684\u6570\u7ec4\uff0c\u8f93\u51fa\u5176\u4e2d\u4e00\u4e2a\u5143\u7d20\u3002<\/p>\n
\u8c03\u7528\u65f6\uff0c\u53ef\u4ee5\u7ed9\u6cdb\u578b\u4f20\u9012\u7c7b\u578b\u3002<\/p>\n
identity<string>(['1']);<\/pre>\n\u4f46\u6ca1\u6709\u5fc5\u8981\uff0cts\u53ef\u4ee5\u81ea\u52a8\u63a8\u5bfc\u51fa\u7c7b\u578b\u3002<\/p>\n
identity(['1']);<\/pre>\n\u5f53\u51fd\u6570\u7684\u7c7b\u578b\u6bd4\u8f83\u590d\u6742\u7684\u65f6\u5019\u53ef\u4ee5\u5b9a\u4e49\u4e00\u4e2a\u6cdb\u578b\u63a5\u53e3<\/p>\n
interface GenericIdentityFn {\n <T>(arg: T): T;\n}<\/pre>\n\u968f\u540e\u51fd\u6570\u7684\u8fd4\u56de\u7c7b\u578b\u5c31\u597d\u8bf4\u4e86<\/p>\n
function identity<T>(arg: T): T {\n return arg;\n}\n\nlet myIdentity: GenericIdentityFn = identity;<\/pre>\n\u5b9a\u4e49\u4e86\u6cdb\u578b\u63a5\u53e3\u4e4b\u540e\u6211\u4eec\u5c31\u53ef\u4ee5\u89c4\u5b9a\u5177\u4f53\u53ef\u4ee5\u4f20\u5165\u54ea\u4e9b\u73a9\u610f\u4e86<\/p>\n
\u7ed9\u8fd9\u4e2a\u63a5\u53e3\u52a0\u4e2a\u6cdb\u578b<\/p>\n
interface GenericIdentityFn<T> {\n (arg: T): T;\n}<\/pre>\n\u8fd9\u6837T\u5c31\u4ece\u201c\u5b9e\u73b0\u6b64\u63a5\u53e3\u7684\u51fd\u6570\u7684\u4f20\u5165\u7c7b\u578b\u201d\u53d8\u6210\u4e86\u201c\u5b9e\u73b0\u63a5\u53e3\u65f6\u89c4\u5b9a\u7684\u7c7b\u578b\u201d<\/p>\n
const myIdentity: GenericIdentityFn<string | number> = (arg: string) => arg;<\/pre>\n\u8fd9\u91cc\u89c4\u5b9a\uff0c\u5b9e\u73b0\u8fd9\u4e2a\u63a5\u53e3\u7684\u51fd\u6570\u5fc5\u987b\u63a5\u6536\u5b57\u7b26\u4e32\u6216\u8005\u6570\u5b57\u3002<\/p>\n
\u8d4b\u503c\u7684\u8fd9\u4e2a\u51fd\u6570\u63a5\u53d7\u7684\u662f\u5b57\u7b26\u4e32\uff0c\u6240\u4ee5\u7c7b\u578b\u68c0\u67e5\u901a\u8fc7\u3002<\/p>\n
\u8fd8\u53ef\u4ee5\u4f7f\u7528\u6cdb\u578b\u6765\u5bf9\u4f20\u5165\u53c2\u6570\u8fdb\u884c\u66f4\u8be6\u7ec6\u7684\u9650\u5236\u3002\u4f8b\u5982\uff0c\u6211\u4eec\u53ea\u8981\u6c42\u4f20\u5165\u7684\u8fd9\u4e2a\u53c2\u6570\u62e5\u6709length\u7c7b\u578b\uff0c\u800c\u4e0d\u7ba1\u662f\u6570\u7ec4\u8fd8\u662f\u5b57\u7b26\u4e32\u8fd8\u662f\u7c7b\u6570\u7ec4\u7684\u73a9\u610f\u3002<\/p>\n
interface Lengthwise {\n length: number;\n}\n\nfunction loggingIdentity<T extends Lengthwise>(arg: T): T {\n console.log(arg.length);\n return arg;\n}<\/pre>\n\u66f4\u8fdb\u9636\u7684\uff0c\u4f8b\u5982\u8981\u505a\u4e00\u4e2a\u4eceobject\u4e2d\u53d6\u503c\u7684\u51fd\u6570\uff0c\u6211\u4eec\u60f3\u8981key\u5fc5\u987b\u662f\u8fd9\u4e2aobject\u4e2d\u5b58\u5728\uff0c\u8fd9\u6837\u7684\u9700\u6c42\u7adf\u7136\u4e5f\u53ef\u4ee5\u5b9e\u73b0\u3002<\/p>\n
function getProperty<T, K extends keyof T>(obj: T, key: K) {\n return obj[key];\n}\n\nlet x = { a: 1, b: 2, c: 3, d: 4 };\n\ngetProperty(x, \"a\"); \/\/ okay\ngetProperty(x, \"m\"); \/\/ error: Argument of type 'm' isn't assignable to 'a' | 'b' | 'c' | 'd'.<\/pre>\n