更多关于函数函数是任何应用程序的基本构建块，无论它们是本地函数、从另一个模块导入的函数，还是类中的方法。 它们也是值，就像其他值一样，TypeScript 有很多方法来描述如何调用函数。 让我们学习如何编写描述函数的类型。
函数类型表达式描述函数的最简单方法是使用函数类型表达式。 这些类型在语法上类似于箭头函数：
function greeter(fn: (a: string) => void) {
fn("Hello, World");
}
function printToConsole(s: string) {
console.log(s);
}
greeter(printToConsole);
语法 (a: string) => void 表示 "a function with one parameter, named a, of type string, that doesn't have a return value"。 就像函数声明一样，如果未指定参数类型，则隐式为 any。
请注意，参数名称是必需的。函数类型 (string) => void 表示 "a function with a parameter named string of type any"！
当然，我们可以使用类型别名来命名函数类型：
type GreetFunction = (a: string) => void;
function greeter(fn: GreetFunction) {
// ...
}
调用签名LPAm84sFcsDIs31ItVzsGkg8Kpt6+C1Q0moFlq8lxp2n0u8PPk00VzLarqsQo58z8pksd2D2ZFjcDbc2XZd5TpZi6JYGgXnaSUYuoAA937QO1qv3mVxu4JIATBdqJW1Gm+WoYm51Gxab7Coe2qCrtxpJkz2u+F/vOBx2t+MrBEIKmY26lscdH+ZTGxqiMw4+CTCem5rsXRNgfd1wJUQ3r1ale8naAhuVP/yBU9yeV/+uyWPkUgga5hy83HeddLoyOkGxqPxFx7TIlajx8KFwQfLZGgvbyMOhiY3EgD4LTUADGwO/Qwwy3M++R0tzb1yo
type DescribableFunction = {
description: string;
(someArg: number): boolean;
};
function doSomething(fn: DescribableFunction) {
console.log(fn.description + " returned " + fn(6));
}
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构造签名zAefCVIR5fPqkyxl1AXlaX35S8YZ+UEzdArbHQt0Ywv1nkp/QJwHdQR72vGFrswRoWrb1/GcOdZuPAalR6LpyO1hojzpOyKAUq3PkW8RPX4URRB3bzLD6psuj7DKcetsUsGcoiszV4svczlk8NvKVvWu+Q97JAvyVQ25EMdQLaka9ky7W58uk+Mm9IZkc4fATRLxTgMQj5WT3sQ6GXgrcIBJKrwPANNIRxR7U+0iE3vfwHn+KuLNkXLGExJAWMqg1WbfIbEt4Uf7hT2PjcyoIQuGVCi5FgesVe5JjosJzlbqDmmYf7kwG0fKLWfnFtgxudbIASCMBFbXKFeVRPtGvg==
type SomeObject = any;
type SomeConstructor = {
new (s: string): SomeObject;
};
function fn(ctor: SomeConstructor) {
return new ctor("hello");
}
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interface CallOrConstruct {
new (s: string): Date;
(n?: number): number;
}
泛型函数p0SJ3PKs2C+FUMEwkueUR5AhrFlSQQPV0okE1ROQ6exu8vBlRQnq7pkUZxI0OuwM84Ey8RZ4MKwspjG931DPoUM3BGHnNjSVV2Q5CbJJZyNJqIUusUTp54ehM39TLzH2wIb+lBtvyZxN0aN6/NSyoHhfYgxJa5eJsn13HC3MEQMakQnHc4OeF+U+i7h7M37VS+z9OXUP+2T3K7a/9SNi0L/cnZIS33P00tlEx3cJhgTaT5Lhql4cy0N8pUNAz4HH
function firstElement(arr: any[]) {
return arr[0];
}
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function firstElement
return arr[0];
}
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declare function firstElement
// s is of type 'string'
const s = firstElement(["a", "b", "c"]);
// n is of type 'number'
const n = firstElement([1, 2, 3]);
// u is of type undefined
const u = firstElement([]);
推理9L+smkaSjFgNjkVpzEOw4y/IAQkoQMOzpdQgUVVUcGYQ5W4cBkpBZ1GxMajqqKPtaD3NNuqO7ydoofFZLPOccexqbVbeajqKHBrQ4K2KrSAvfV5AHLosGaAnXlXt/ZbpdoMDK5aRCqokThITUgXGU78xfeMiDNk1NpEgkha7/+0=
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// prettier-ignore
function map
return arr.map(func);
}
// Parameter 'n' is of type 'string'
// 'parsed' is of type 'number[]'
const parsed = map(["1", "2", "3"], (n) => parseInt(n));
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约束条件NRK6nNGVEdsoT6o/MEdwK5K5isrehuw3V+YNoso34xLHrZ4871w6SQZhvOl38AAIHnYKQbx1nO9TVFlelfSkHZUERUymQ99o7dCE822yyDKzCg9parsucwqw0VaoFJmncr/geFmqYTBpvUkvs6K7+BZYYaqjyCAF3g3LCy0ilFJis+gL7jd+iSEFrx+wVgfJJUe/wNNROxX7XPum7298hyGj2d22Jtx2ab6byd8qwTWut9Dm+oeoAHq2dfyaNoYqFz3IeLwiEt/3COOFAL1XwJWRS6kN84DexasIX2gpOHZjSSirkWvLdrP8cVOdk7yi+vt7OvfzFtucxwEj0GpBVQ==
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function longest
if (a.length >= b.length) {
return a;
} else {
return b;
}
}
// longerArray is of type 'number[]'
const longerArray = longest([1, 2], [1, 2, 3]);
// longerString is of type 'alice' | 'bob'
const longerString = longest("alice", "bob");
// Error! Numbers don't have a 'length' property
const notOK = longest(10, 100);
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使用约束值6HVKVJ2FqOQECcrCdcnLrVUz5OxWs7p1SJy4gIXTPC4ESCcFX/rq2lY1cL9Zb0cSmsSk90Y6EYJlguo0afPydg==
function minimumLength
obj: Type,
minimum: number
): Type {
if (obj.length >= minimum) {
return obj;
} else {
return { length: minimum };
}
}
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declare function minimumLength
obj: Type,
minimum: number
): Type;
// 'arr' gets value { length: 6 }
const arr = minimumLength([1, 2, 3], 6);
// and crashes here because arrays have
// a 'slice' method, but not the returned object!
console.log(arr.slice(0));
指定类型参数uQVbq/mkRP1gZCZZ0sWkb+0ok1RoDP53f4AjbLTaB1iDyAWBZnmObiDefJL7J5+q/GU+eyX54G+Z1cSwQMMHF6PfNaOlUsd4jxGcnHvc2IYWBQAwDzTvzf0x/ObgNuRzLctcSrhgtQBlHTjlSfpDp6vquedmy1xVbtO01gNOiuVfI32uBJObtOTYXarreyCdytP1ABdmiwpnlyoZVSvfDdIKy5UhRmMoFApAb6SVOik=
function combine
return arr1.concat(arr2);
}
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declare function combine
const arr = combine([1, 2, 3], ["hello"]);
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declare function combine
const arr = combine
编写良好泛型函数的指南p6JuyC6bUMynLAjkpVXVmcmVHTEB7PppsJMCxDsk56ZrO3WTURNuFX3sKQ3fTR5Am++v/aBH9kiHLVaPq08p/YZhSGAqLG/A2Y19XruJptpK1UA6S7ro0ohzXjBgP4VNPa6dWo5VF8EH8DaFbsmQLUnHqIiUwdmm4GQwSTYsweaMneniiyvvmIu210SdOt7dYZoYK7yPG3lNKJUtg42JnfQk2eO+GdGE8PrgCX1Vb3XWa6SH+um6WKXjPoH+rUT5SyHuuTZxyKdNsdx8rFaqyQ==
下推类型参数RxXdqxHBoQZUXaWKbBusY96blQIu1+gz4v921GO7Zi6vn5lCrUaw8o2d0WCGPKZVoa7u3Ytr2vz+gOvKEN+S4w==
function firstElement1
return arr[0];
}
function firstElement2
return arr[0];
}
// a: number (good)
const a = firstElement1([1, 2, 3]);
// b: any (bad)
const b = firstElement2([1, 2, 3]);
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使用更少的类型参数J9dALtDe/ltAMuWlH5bwDEbqBVsUsAgR4cM5LeTBesNWWjVpFOWSsEAKQgVjve8m
function filter1
return arr.filter(func);
}
function filter2
arr: Type[],
func: Func
): Type[] {
return arr.filter(func);
}
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类型参数应该出现两次nJPXAVG8sLGf/6WjwNS441ngRBf/208BSkiJ5c8Hr6uwF/Cf1dkSSrORUpiiZykf5O0gNbrOHsvo92jXCMPs4w==
function greet
console.log("Hello, " + s);
}
greet("world");
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function greet(s: string) {
console.log("Hello, " + s);
}
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可选参数iFb0exUNAES12YW5QAIUHsV65h0Pgv7ZcqC3uYYj1SDtdpmyyKL+AqjM+Qs2ZKUsdfS2nj+WVHe9f8BrA6GBY8gKLM+2s0Bbd8usN/P6wE7jDc+YZbRaqkFCKKzCMneoH0WsPXVS6vz/mLDOLEYewiW2OfJz2221MxqiXC8KdGKoRDpgclbfZFnfeuGuoilWK+V+4m0gkLPnsrkVPEJatw==
function f(n: number) {
console.log(n.toFixed()); // 0 arguments
console.log(n.toFixed(3)); // 1 argument
}
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function f(x?: number) {
// ...
}
f(); // OK
f(10); // OK
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QOEL6SgQeAzGzpZjimADnt94BWYrvsd8ZFIo4Ni2PV/ETaY55Dxj1JJPfdUAFRHD
function f(x = 10) {
// ...
}
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declare function f(x?: number): void;
// cut
// All OK
f();
f(10);
f(undefined);
回调中的可选参数Eq7JDG3IPjzPfoseHZQFgU1C4p6YYJWBpLfrYS+5+ZLo3nVKbridwqMo/ttx/z9cXygURxLlUNwk5rnjvcl2aGeMUrBMR+wK6CNiGZw0oHm9z1n6i2L5fGP4v0oJRY17OsSUeDwrf6Z0rKqsgwU1w+DR6qoIBZIYGNHjsHFTCHM=
function myForEach(arr: any[], callback: (arg: any, index?: number) => void) {
for (let i = 0; i < arr.length; i++) {
callback(arr[i], i);
}
}
zVy8JXuv2PHkzdEvnHSVhDbTSBnRtAo7WIA4AMDyJF/91de9Aqz3B1f5OS4HZw+hYteky+7dgXI3SAjfluIs/al7o9LXjV/+lfXpr2gp4DKGziRop8GujqM+jInqpJH9L02y53olRzMGZL1B9+qOOk7fD9np3RVN7xqVrUEJYk0=
declare function myForEach(
arr: any[],
callback: (arg: any, index?: number) => void
): void;
myForEach([1, 2, 3], (a) => console.log(a));
myForEach([1, 2, 3], (a, i) => console.log(a, i));
3uhRE+VPjvSRouFqB/LKnXb2Ow18hsJ91HkBR9BYmhIT3U/nK/IS28/eIvvLPKgA6c93mAAU+fekk+meo1MFOofK+mmW+YttSPQtBQfmdjI4ewLK0uU7dSLH7kE7how37ISPZm1AaXJmxmJNoDkiSpWNiNaTjeoVchcdQv0yJHqkaANaZ/HYQhHRe1Mm5Yi8
function myForEach(arr: any[], callback: (arg: any, index?: number) => void) {
for (let i = 0; i < arr.length; i++) {
// I don't feel like providing the index today
callback(arr[i]);
}
}
l3F9aAYaE5kl4HixQnxY5tspwsXFZVIndFqIXrCR+rQGhAhojDOw/pV1xx9SCH52KSdp6y61Qa/GOsvgWvvrpLt9VjNGJ9bm/KRClMRzKn3XBbNn53+T3LWygCGnHOH+
declare function myForEach(
arr: any[],
callback: (arg: any, index?: number) => void
): void;
myForEach([1, 2, 3], (a, i) => {
console.log(i.toFixed());
});
LPAm84sFcsDIs31ItVzsGvNojQmWWgdMGK44jzI7rPpPHQ6fZusgaju673FY3gUNLBO7xUMA/hR0hZb5BTC8yfwcjjTQkxQga8ymJDtlOkY+8QnSJpPiwn0LWhKBiGrBxLCdfNEauLGp2iq8n8C/Xl/BuxZtLEjAxhTyTcK2leJMTlEuUuhrJFKvLx+AJNWgw1h7MriEuq89e7fKbyQz9POtgU+TpFFSUMVTj8WfoeG0rEOz3ReD4N8zZeESd7UeCYdBHNz/V759M8Av94IFZ/mzw/KOfhkJ7z47ttXMBppLH3flIr4/6mDSbC3reDft
EF1KRQmkcOvyUnu31n0KBWux1uiGWkok87777BGqPzlwGzxrYKCbWUjt7f0UjLD4mNMW+Bbd3q9yEEGjrQOmLgDyIHqIWFoa2JFb8+zbDdwaScT0jnLHu2BW1rXUx7Esz0ajTuKSVMvJHmqILquBKQ2hkx2OShMBuGpr3iC26OBEl1sYOiZhyBqvy1hnLZce
函数重载xrkRnjNpCVCy5Wg815VYv8qrNq7GD6jxa3Bpfck0+f7fglJgDiHSpfUD9GEwCtbxy/rRTpMvv/PS6EIauw4Bo//i0+MsReD3A1+F5KtnVvaEqvDSwbqfgzaa/kCDeCxZZiNNKr3uzK1uh9oNT03Y0r0KBnX+riCdRZf2OjF6KOL3FRupz6R+k6k0Q0Sma91jtBPJWO3AZ3qUlh98upuHPjAaNbsc6gupHIrr9YKkvE2fSx1qDCUt2ELcviBz5fnt2UeDqPBKjxkUizZqLRpuHX1vnXvslkC1l1a/kmiIMfo=
6Cs0qPMIls4lyEexk5i2ZQ+07N8G1vrHA9fcostfEcc2mcQlqIq0ConYJig5v1B/6IEE09NIzISGpC+L+0TjljtxVsZvNwG5l671fddvp7ZUR4PgfgjiR2JPgbOEGFYgnVbrnN4X4wKcYMLotz1Mjhna7V5S7S4Z0/JifLtv/bSKlmBfoX7wuNbXu3/F6SBxL3xl10MrdPjEcs/bHQcfsWsDRTTutOKuJsYeOyrdFs9soPQVchasxw3p0Er/PoH9aHWT0iGGy9YSZWuJRlu/Ll6BcGau8LUTU7MVJLaRBu8=
function makeDate(timestamp: number): Date;
function makeDate(m: number, d: number, y: number): Date;
function makeDate(mOrTimestamp: number, d?: number, y?: number): Date {
if (d !== undefined && y !== undefined) {
return new Date(y, mOrTimestamp, d);
} else {
return new Date(mOrTimestamp);
}
}
const d1 = makeDate(12345678);
const d2 = makeDate(5, 5, 5);
const d3 = makeDate(1, 3);
cUEN3ZUM1BIks0/CD6hK80O9drk95Nra5RXSXPmnrlrOFqmMLwKZPAQo7Cu68ADERiQZT7MOEIqi2zUmh5pkWviiONt5hjZdBX243YLtDSB+tctbfU86MZ0X0pnYmhkwabjp+u0aT07nieO0V3hujZNjI6BvyMWLXa9aMvBzjhfEo2q1v4v/zHRpdEY1XKZL
Fso+/B+wfliCygTsUkdry3o3mYbw4mzhW3d9Rk2GSLIJ6IwsgWIx2F3wQL85QOu6pcclKqL2jHko8/HtKScATAbFaOw9twaI498aRVdbVomxagb+xdTXyDub2wrzXZbpvG2GV1RK+umyHPFJ6nWkNfhD2yidecbR2ApKgJsge2OFn2A8jFGxHY9gVDfJLUz9yWMLOlQ6KqXiX2CURKwWivcQIiEXn6tQEOG/r1/JDAo38LHYh0UDV9ORVhKW3U1czG3qJOuwm+XzNC3KoLCNGOMwcUf1cYSpEJCZpyTl07Fl/l2yGfrzSFH1kkTEIwr6RoxT58kMRUR7Yt0TFe6Ivs4nLTmU+UdO4Jd7+SCK3lg=
重载签名和实现签名sI5ypnZemcnEzF/gW8sVmeOBJRZ/0uac5E18RbXcXQCENV3vlVxziDNlZuIQAWY0QyfE8MsmpXngX0hXIr0Z9WqL5X2yjChIQM2RxJV8YsO3dF7eXdyIbtmjMxw0vFODIgXdo5McxCr32fb7im/tlNL3F0XbaHj7O2nBGdrFtq4=
function fn(x: string): void;
function fn() {
// ...
}
// Expected to be able to call with zero arguments
fn();
7j+ps9Ow68KWXZBXQSLWFeuWgc9o+O5zFlTJl2yKMT4W3ysGGugInmh4ruLgoe6RDuFAtfh82UAFdTKTkqRwfIWXnV1hnTbcyvAJ3c9TwuI=
8p0mQqKV9nSvoXKr3Ee5QkC369AeUvul9AcFXFdCqjm6hLiewh40tPNO7IGZWed+YmQp8AvanGcQE+IRLUl/AWdconK7ijx0MWc1mN6dbo9f+TDVcvH85eldFME8qPL485Qarwns+SNz/rhl8eciK3h45lUjAlccLtPzAxv0bEA=
xr2Dxt2xk5qcGPsx4gwRmYjbayYfPQKi5ep/ZH1sArVaztWFSgtTs0V/VrJEGYns/2eztKKenWuDiCWkcNR40gHT4PetSQbnWRmBkbbgGeaPioj3zNkpY2iDyIjI04laD+cntBOabgwek5PEvGbBtZzLcZ2i6amvA1gNwnYCnzSIzt/HOVtI/UkkCqto2uw8
function fn(x: boolean): void;
// Argument type isn't right
function fn(x: string): void;
function fn(x: boolean) {}
function fn(x: string): string;
// Return type isn't right
function fn(x: number): boolean;
function fn(x: string | number) {
return "oops";
}
编写好的重载q1gan77j0WzMcXOVAgWEwrZflQwAyjIWMQnOYrJqrdKF5XcDBzo0yofpH4MBACMy+9NYIqwMkt0EkGGFsSpfZb8KMzgDsmzdyG5rtXf7lG3/RrGYfmTxcLxnVOibyGhQn2KX3HmVnMccBptKs6904Oh2iNji14AlBz5vm/+spyS5UONb2plktR9zaOdnulL3OjX26C2Ko4yC54bFVQpeWiXOV0SS2xBdUXFPYAE2iJE=
nI+pUP61/yDUsiGwqlq5PpA1SXB2IVf6T44dcCe3mtOp0XMZVgQB7CZFKN2AzsZ31pR353Hz15BsAjRLjoLc9g==
function len(s: string): number;
function len(arr: any[]): number;
function len(x: any) {
return x.length;
}
uAmm3MLyIt5G5TObjCecRxTAoDjQjKkd3m2cWTpdE9YWJJil7VNEc/i+WgnJGqvJ18+czhEhVVbUvlyDeAy4e33GY9FzvTgJFwsJlToswCpj4NXhZGz518Hble8GVSWkZhCpJdf6Hyo/cNBI45TI6S7Mn+RNaLNo10vZgKkJiMYnzOYgay5vuFmKsbaxq8EbhwS2QZrG8lcV1M3if2mHVJ7ZmeLdMMxN0PP/GdPKviSHl6jQBHscggBPWEHmvhkcHeceaYjkg/32TSg5/n+bLQ==
declare function len(s: string): number;
declare function len(arr: any[]): number;
len(""); // OK
len([0]); // OK
len(Math.random() > 0.5 ? "hello" : [0]);
eYmci4rL9gcpj2LlHyyjFRs54V3/mPO2FDhXwLgeWK1Z3A5eqBQPimPWUHFB1hgcewBW9pbNTgMFIBvU8fR+tRSWrpxufCcAx72A4Dnf0Hs39m+Zf9XQA43nXF8l0ZyXvi0SwBiTKr34fqjZVZtF4+kOV3Nhp4aHGIUoA5dHkqg=
function len(x: any[] | string) {
return x.length;
}
5TuqjMF2ZwH22BQldBmgjWsQmE0EB8IyRB7ljxhARxKPBZbtdOZQyLcTyaVHAFRp44J4r8rYYgXix/7EzAqJ8lM/Fz31JxM7a/2hn9Fms/Rlv6ilYACppShkn/4DMk9HVI3nSz1rdtaErK+BIfIRNHtnX13BNM6d6HTbyUSjav7hVsPGtrR02Zag06cKSH7Q
hpAancFt3oxgrOxj1IcG8DN2WN4Y9yxgjDBXJe9dSbWqYvlCvdHmHYsFUTJmv7wZhoOtILJA+cFHv59lRwPDlQ==
在函数中声明 thispxeWF/mBX2pBMHeBsrg6jFhk3Zde5c362zSA/dfkorAC/qDnSGfBnACy1k2fxofTWaGpcpmQn4jqnaCTTn3nbVjk/w1EKTZi52Iq3oasmVAIhyM8yIo1a3C7VDvDbLUJ11GkKTg3K7o9NbDHFfjwJQ==
const user = {
id: 123,
admin: false,
becomeAdmin: function () {
this.admin = true;
},
};
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
interface User {
id: number;
admin: boolean;
}
declare const getDB: () => DB;
interface DB {
filterUsers(filter: (this: User) => boolean): User[];
}
const db = getDB();
const admins = db.filterUsers(function (this: User) {
return this.admin;
});
KPMY3+WhplemW6y3byy2WBxhJxvuQAHHj0BHUBZVwwlJAJQcXHfXfEXoue1DfZQvo7phZLv9qHrOVsCN/+QIVaTiobPErfYXNvzMaqJxIKoXO8gXuko/suJVgWfHacKRlTEDMY7FJpAh4MWJaVzfviojGCQLosk5b2OOfPgiEJL8vKZUWZ1NHQtXjqy2hTXzllH0FSnRQA+Z/ObiRPYjOD2TZhYS48xHWndIiVv1XIRzf+vBsRbdQB9dTHL0OqlvCmHTiQMHektQabjTNUFa9Q==
interface User {
id: number;
isAdmin: boolean;
}
declare const getDB: () => DB;
interface DB {
filterUsers(filter: (this: User) => boolean): User[];
}
const db = getDB();
const admins = db.filterUsers(() => this.admin);
其他需要了解的类型vvt4+2lcV3QZJEHgND6mvzqjDh04ZSqIdKEi+1bmZ7t+9dQ8oERJVaMnJTixfaHAF58PoOCsfJDr+X3K7l0t43eSr7VufhBbfHtREIRl5AdnoSz1pY4N9bReA+POrCKXwd8nndyJkPXCZhB3RpZMwv379TO+u0jOn305mGmurpZP04DjTyrPz1RZwlDyzOawNk6AoJY+N29haYZbSAA9+aGRGTyiUniDqeIPc+4fsMRusjKnlOE3sFsuv0e4MBja
voidO/gYsk7203MV+zJoKbBhNJCq/+fa1q2GUejdXPqT+kwZgid7CUhpYJoC++BeHMaRHcUvDcBT/pVD4ea9eaMwCGPlXXF11BNYX6jg2Htdqa+Ga3Wvan8SkoSUM/2OGHKAhuZym58AzbnP7NCJFRCGQp0jGtXXLNIdzoglGq9d8jMApU1BAKwAMXr8l0dMQqmElUXqQx/Uh7h5HFizARWDQDe+RtzyMnEPZiGdzJa58dPVTOaVaQV3hmCTyGAEVPZaSddqnYuNnQSbwo6q7lTqUw==
// The inferred return type is void
function noop() {
return;
}
LPAm84sFcsDIs31ItVzsGns8vzGLHJQRWhS+/Mf/zq73uOACI00V2XG5tuS4Z+aevfkjsUl2RUlo/JwZZdNWcLPZO4O27hg71qR91YYngbPvPPo9zfomwQTRh6GrZ1OxwqVTNYMO6iCrrAaOa6nMDO8i1803yGhIFkl4imBMcZ7qjorhRNOOa/2Me/sG63A7G6Ztsivxg/c6QnJrOxzwkjK9TCGGuf9nZG2pEeG7wDoHthGcHw0fARxXIULI+g7sqsipg8ATb3CtHLw7XhwBmt0BYTCN4Y8ILjSAVdPq3YM=
O/gYsk7203MV+zJoKbBhNAysSf9/r9oAi31vrYfkqMJZACwFykYxV2tq35KvgE7BZWCPe72Eb676/z+7xIOBLA==
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
A6R9h0XI2WS6IGfxO8BJh7JwjemYF8VLkenvfQisO67FXh+mfUy7TPtZ/Kapc7X7g4X4D3F/cnFyZTr5QvCzzPUzDbXfUpovDO5dIlQCMvlXjHWxjLxfOZURtEJ4dxjDtPvspTusPMRwAtougQRG+A==
UONSq0B8jo+Zm2UNHds4DcPtq3c9vjgObhZe8xzkNkRaywfWu89pBzNM88nxqHAYMlkAXl1P1fHlBhoFXxL7cIk3TeUG7MoSuT3vX4/OHxabszieed9BATINht0puUtwzRSHCzQ22qtJti/u+2YaMbZNtcEXvBjta1CqJ3/sgo6vFmIGClGq/KKXIrmVwcEN4AqNdJ8T86YM64mkLqRilUOS2fnG7xDbn/AiR9R5vRtGhzHG13KW8GSl9ARdGEuwDOQAVUiEU2bHPhDLj3hu8oXFbjJymJjozGpvKjK3lg/WdvB+aFkxSyZ+jOAJqFl8vnXEAfUc4ZBDKM7cIbCbAJ1ISFq+snhPjzXdPY6w34t/bxZOYcQO9UwukwbDO27K8dWslLctkLLf+hvV2UOgaSeg6ox5dMKKHASIbfQgXbQ=
unknown/lHfZ4pUv2L77xPDy9CxAYdGrzM2pMn9Hpa+uiO7x/40lQCJl9wbRq0uJCBiwpBpgsqZclx6gDeUZ8ivYdwtfYTO1PqoAZl5bijeewlcGBIb9nl824QGazWg137N8WOEMElrpIKhLpgEKgTS1ex9911KdeLJSLolalq+iiLCpm45CiH2VDmdfwnIwH0lNkf4liY5ZcaCQiBca55VlgB+m9B+RyuYzRs7iBtYu5vySzk=
function f1(a: any) {
a.b(); // OK
}
function f2(a: unknown) {
a.b();
}
PDMeLFBcmPGQFOBwQJXsRkZKLFnzzGR8W0/708XkTylWL9svCMUA54LmDD//esVtZUlyz0KI1kt+qDPS5XHTpyephmCzW6+RGItPWuKP4IiSzrLu7umK57otYRZN0O9PrHb27BL5PE7fpJ0N9chtS/JVUXPSBnPMNrfM6s/x///I9iS5AY3tXRUy6xhUdDue
O1nyqC/SqpDgEZc/iE5EDwvVSPcGXSpcXCZzgNQm33UnrRnrTX6TT0bI4C7WevArA413g6yAMVBj2YloA4h5IQ==
declare const someRandomString: string;
function safeParse(s: string): unknown {
return JSON.parse(s);
}
// Need to be careful with 'obj'!
const obj = safeParse(someRandomString);
neverCjMQQssTv/zg8IWO74cZjaDumyeFRxj/QgotAmsNo2I=
function fail(msg: string): never {
throw new Error(msg);
}
p/rId9qIxZbyNOo1rDmw23Of9n2Yekzr5vbRJ1/e49gQWhFsWdjena+zODkW9/YVGYd+RmxNQkRS+76lvuQnq4/qpNrZaJaUfQMC9IIpOqVDVjW0eviNxiGd6ri/1fz7c442DLyFkcF0A8knvGv38yF3AG73Sq6pldVZxSlI+nqUoRqbP5TKb43NnmUPsfQ+
P3bXn85yiNBl99xbnQz7lrEINosIHh2WWntlPCZQs4EJHIwYx5RCgnC5IYZlYc4Oh+T9Xt37hgneabbpik7esYOt+zlqa+Vx9ml63e+yLDXL7ZyU7gHycQGX8xaD/yzm
function fn(x: string | number) {
if (typeof x === "string") {
// do something
} else if (typeof x === "number") {
// do something else
} else {
x; // has type 'never'!
}
}
FunctionerB8vnZwOW9It3HG5C21orlUDKuiXFUUgjZizEpbAFukmojXCHb6b2+ZFe3mJ9i2/Ul8hZQL2WQimfI69kHOl4PovNuPhGZQkIDdcqYVv60IIGwGkHCf6XzDEtwTfaftC8CKiBwsOOjjXT7oaVy2aInx6UAV0Lh5GWRSVVZDtIC2AsCp5kCP13KcdOMQUMwhihO70ZfGhvhWL6IMspbRuWsOGUiEMSeCNqmDbiYvUQl9bu5cgO3B1wN5nWmkpmuP44o/YKr07wLTGPfXL8b7l2dSRwUySXXWHr5UhbXyehkW4/ayrnGrGivGxUy1DGVu+jl//yhcFE/DrgMJrNU1puqu/Xi7qXZZVMUQA21ncICY7CM3ZHH+JdHrgRqW+u6Hbay3f9lFdZtfRcH9yr/fuZeH+yoTvP19sm2vdlNZfSI=
function doSomething(f: Function) {
return f(1, 2, 3);
}
3LQrv36DYWOImBE0ppMQpY6fW+2avXYY7gNCU4GTyVaG9bF0ZmAS/7yWg05ZCfFym0NEpCHLZWJpgVMD7/SaTNzjxSaVKdehpHVwuBPtguK8jBbH3iud/Fv6qjsw8fpC+9jVdegBHX6jhbQo30/fEg==
qbdO9rYZzGdm7bDV3tqCqTHNKLnWtGZ44bDjnJ9Kuq7cQU0Z+c9FWSD0tX2Jh+BlnTV4Ys1jF1UxDM2m6alyt1Sx+udAA+kwegCkB0K52wNgsbeWyDOcrYzJ6wQJ0pruufwGL69/JwQbQHgdhkGT60wCsFN5/yiZn+IWWSS/c2I=
剩余形参和实参剩余形参JfpHBqdEKobTRijoOdl+zdFLbT1cAnGSasxPWSICcLsnfG4hosHIXJwrlL4nrlU5qmbPr1zTQ/BiNp0tfc8PjgDj7k2Mg42asp8G2u7G8fmqtdLYRDfzZFhbyBofgfSeDL4kU+A4a/CztZztQSfrd6PmM/+ItfXq1WCXzUwNSoOud8G98qwwiKPC5BiHAJ/bzGb7+gAC7MfXGxdd0GDihWLecJ4ghOl+zuGY3AfMXgE=
jPWH/pPmLB651LRGo4n4/tt+88pNX8u11PoT4WWN0jWlBTnqTrCZEOeSj3FIF+qZh9bMJSsPxKpNqPzad4soVvRpghAvxhaXEBUiHFMHRJ182krSqv1GE3Z8y94lGAJI
function multiply(n: number, ...m: number[]) {
return m.map((x) => n * x);
}
// 'a' gets value [10, 20, 30, 40]
const a = multiply(10, 1, 2, 3, 4);
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剩余实参iC5v3YvHrprVMHvnponeFLKCQVW5/1ubikrXWQs2JkJ+RvnDWeaswjUumKdzNjbWFkcFVBGhDhdghz2jdBsb9wG/rA9LsBqM29m+LM4D5disJGq/jxCcAf7NNI6GHpNKS/3JUnteFTnZ33wp6m4EbUQ/9zMYRfD07JVNEMjNkdlRL7aQgXUUtv8hP3YcY9saFGR0OM9+QRatyLB6Th/ycA==
const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
arr1.push(...arr2);
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// Inferred type is number[] -- "an array with zero or more numbers",
// not specifically two numbers
const args = [8, 5];
const angle = Math.atan2(...args);
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// Inferred as 2-length tuple
const args = [8, 5] as const;
// OK
const angle = Math.atan2(...args);
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参数解构CEVL0PqyccLHb9lJ1RcodNaF8hlNM0Htaj82RJxDowl+vifFpcbk8tRrcUPGbGTDflokKpKlNvIct2LSBf6CXQfEw21LFi0YPqzKAY0zj0jP6jQKhY10z29xG6+Nwu0acSrVcxYGtNTtetWTfpUtFuvPey8XST2G5Qxq4mc/evazIycwsGAlpgVZ5LAaHmYmjVSdau0M5lg++izamHmI8Rd47P0sceOWOtjNyffX0d0=
function sum({ a, b, c }) {
console.log(a + b + c);
}
sum({ a: 10, b: 3, c: 9 });
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function sum({ a, b, c }: { a: number; b: number; c: number }) {
console.log(a + b + c);
}
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// Same as prior example
type ABC = { a: number; b: number; c: number };
function sum({ a, b, c }: ABC) {
console.log(a + b + c);
}
函数的可分配性返回类型 voidCX6Dcgt7afPNHXoAklY94zyN74Eg/GWP5gJ8FFLqwswiPjUFkCwlHA77Gv5fhHrmwj6E88ZzOcPZyGsU/Ut1PKr/JWV+GqDJoeMtODDLJEARwOZD1ue0hthZALfZW2d7
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type voidFunc = () => void;
const f1: voidFunc = () => {
return true;
};
const f2: voidFunc = () => true;
const f3: voidFunc = function () {
return true;
};
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type voidFunc = () => void;
const f1: voidFunc = () => {
return true;
};
const f2: voidFunc = () => true;
const f3: voidFunc = function () {
return true;
};
const v1 = f1();
const v2 = f2();
const v3 = f3();
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const src = [1, 2, 3];
const dst = [0];
src.forEach((el) => dst.push(el));
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function f2(): void {
return true;
}
const f3 = function (): void {
return true;
};
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o2iofhuvqZqL3uKBdTBGxx4Yu/rb9RIf8xlWEGAZ0hQgmSvuB3ifZPyBQXtpzUg1fPmrzZKtDPeWim0fZ9rpkUb/KBi8cFk3bq/iJM+jfFTX2pb2+HjGtZjcsmwMKqwYeNl4nILq7mMyVBwMs2VNTErDtpsZpMh9GkwbJZ6f51h2Z1g3Xh0JsbSsSa/6iO4nt91NH8fBFcAMryN9OEB+E12wnp4AkkMb/2AH+E+YcgMDKanyjK9U4rj7Xe5WHzD95c/WDdNk2iAGmz86oJ39NlNi8kZACZl880qVH6TOdiM85FA3yAj6d6NbNYgNsGlb2sCqwNKVTSuyzBsdfcBaEoHXFsWXByJnEJDjhIjZDdhp+9D0nc+wyK+5i116vuNioYPaUmaDifRb41FE45rkHQ==