// 类型别名
type PlusType = (x:number,y:number)=>number
function sum(x:number,y:number):number{
return x+y
}
const sum2:PlusType = sum
type NameResolver = ()=>string
type NameOrResolver = string | NameResolver
function getName(n:NameOrResolver):string{
if(typeof n==="string"){
return n;
}else{
return n()
}
}
// 类型断言
function getLength(input:string|number):number{
// const str = input as String;
// if(str.length){
// return str.length
// }else{
// const number = input as number;
// return number.toString().length
// }
if((input).length){
return (input).length
}else{
return input.toString().length
}
}