typeScript学习-自定义守卫
typeScript学习
自定义守卫
function 函数名(形参：参数类型【参数类型大多数为any】): 形参 is A 类型{ return true or false }
class Customer { pay(payMethod: BankPay | MobilePay) { if (isMobilePay(payMethod)) { payMethod // MobilePay } } } // 自定义守卫 function isMobilePay(payMethod: any): payMethod is MobilePay { return payMethod instanceof MobilePay }
function cal(num: string | number) { // num = num + 10 // 错误 if (isNum(num)) { num + 3 } else { num + 10 } } function isNum(num: any): num is number { return typeof num === 'number' } export { }