If you need to pass a function as a parameter, check out thefollowing article. I wrotea bookin which I share everything I know about how to become a better, more efficient programmer. You can use the search field on myHome Pageto filter through all of my articles. ...
//改写前: function consoleNum(num:number){ if(num > 0){ console.log("数字是正数"); }else if(num = 0){ console.log("数字是0"); }else{ console.log("数字是负数"); } } consoleNum(4); //改写后: let getNum = (num:number) =>{ if(num > 0){ console.log("数字是正数"); ...
In the example above the arguments 4 and 3, as well as the returned value 7 are all numbers.Now that you have the parameter and return type information, you can easily translate this into a TypeScript function type of the sum():// TypeScript function type (a: number, b: number) =>...
同时K需要满足约束keyof T (keyof T 代表object中所有key组成的联合类型)// 自然,我们在函数内部访问obj[key]就不会提示错误了functiongetValueFromKey<Textendsobject,KextendskeyofT>(obj:T,key:K){returnobj[key];}
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> ...
function combine(x: number|string, y: number |string): number |string{//不变}//function combine(x: number, y: number): number (+1 overload)console.log(combine(1,2));//function combine(x: string, y: string): string (+1 overload)console.log(combine('hello','world'));//报错:没...
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...
function fn(x: string): void; function fn() { // ... } // Expected to be able to call with zero arguments fn(); Expected 1 arguments, but got 0.再次强调一下,写进函数体的签名是对外部来说是“不可见”的,这也就意味着外界“看不到”它的签名,自然不能按照实现签名的方式来调用。实现...
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 student(fName: string, …remainigStudents: string [] ) { return fName + " " + remainigStudents.join(" "); } let allStudents = student("john", "sam", "reema", "kerry", "jem"); If you look closely we have given n no of arguments. But in a function definition, we ...