function error(message: string): never { throw new Error(message); } // 推断的返回值类型为never function fail() { return error("Something failed"); } // 返回never的函数必须存在无法达到的终点 function infiniteLoop(): never { while (true) { } } 复制代码 1. 2. 3. 4. 5. 6. 7. ...
We used theConstructorParametersutility type to get a tuple type of all of the constructor function's parameter types. If you need to access the type of a specific, parameter, e.g. the first one, you can use bracket notation and access the element at the specific index. ...
function add(x: number, y: number): number { return x + y; } let myAdd = function (x: number, y: number): number { return x + y; }; 2.1.2. Writing the function type A function’s type has the same two parts: the type of the arguments and the return type. When writing ou...
functionaddMethod(obj,name,fn){varold=obj[name];obj[name]=function(){if(fn.length===arguments.length){returnfn.apply(this,arguments)}elseif(typeofold==='function'){returnold.apply(this,arguments)}}}varperson={name:'zhangsan'}addMethod(person,'getName',function(){console.log(this.name+'...
// Argument of type 'number[] | "hello"' is not assignable to parameter of type 'any[]'. // Type 'string' is not assignable to type 'any[]'. 因为两个重载具有相同的参数计数和相同的返回类型,我们可以改为编写函数的非重载版本: function len(x: any[] | string) { return x.length; }...
除此之外,函数类型还可以使用React.FunctionComponent<P={}>来定义,也可以使用其简写React.FC<P={}>,两者效果是一样的。它是一个泛型接口,可以接收一个参数,参数表示props的类型,这个参数不是必须的。它们就相当于这样: type React.FC<P = {}> = React.FunctionComponent<P> ...
}elseif(typeofx ==='string'&&typeofy ==='string') {returnx +y; }//处理其他情况return'Invalid input'; } console.log(combine(1,2));//输出:3console.log(combine('hello','world'));//输出:helloworld 这里有两个问题: //问题一:鼠标移动到 combine 显示://function combine(x: number |...
function getName(n: NameOrResolver): Name { if (typeof n === 'string') { return n; } else { return n(); } } 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 字符串字面量类型 字符串字面量类型用来约束取值只能是某几个字符串中的一个 ...
function scan(): SyntaxKind { startPos = pos; hasExtendedUnicodeEscape = false; precedingLineBreak = false; tokenIsUnterminated = false; numericLiteralFlags = 0; while (true) { tokenPos = pos; if (pos >= end) { return token = SyntaxKind.EndOfFileToken; ...
When calling generic functions, TypeScript is able to infer type arguments from whatever you pass in. Copy functiondoSomething<T>(arg: T){// ...}// We can explicitly say that 'T' should be 'string'.doSomething<string>("hello!");// We can also just let the type of 'T' get infe...