message.error("当指定开始时间时,必须同时指定结束时间");return}if(_state.end && !_state.start) { message.error("当指定结束时间时,必须同时指定开始时间");return}if(_state.end < _state.start) { message.error("结束时间不能小于开始时间");return}consturl =`/api/query/query-call-over/?${pa...
message: string; } function handler(r: SuccessMessage | ErrorMessage) { if (r.type === "HttpSuccess") { let token = r.body; } } 在这个例子中,handler函数中的r的类型就被推断为SuccessMessage。因为根据SuccessMessage和ErrorMessage类型中的type字段的模板字面量类型推断出HttpSucces是根据SuccessMessa...
randomValue =true; randomValue ='Mateo';if(typeofrandomValue ==="string") {console.log((randomValueasstring).toUpperCase());//* Returns MATEO to the console.}else{console.log("Error - A string was expected here.");//* Returns an error message.} TypeScript 現在會假設您已進行必要的檢查。
复制 // 声明函数返回值为voidfunctionwarnUser():void{console.log("This is my warning message");}=>tsc=>functionwarnUser(){console.log("This is my warning message");} 需要注意的是,声明一个 void 类型的变量没有什么作用,因为它的值只能为undefined或null: 代码语言:javascript 复制 letunusable:voi...
}// ⛔️ Error: Expected 1 arguments, but got 0.ts(2554)// index.ts(1, 21): An argument for 'message' was not provided.getMessage(); getMessage函数接受 1 个参数,但我们试图在不传递任何参数的情况下调用它,这导致了错误。 解决错误的一种方法是将正确类型的参数传递给函数。
I have reduced a problem with TypeScript to a simple example. When trying to run tsc, I get the following error message but tslib should be available. $ tsc --noEmit --project ./tsconfig.json index.js:3:8 - error TS2354: This syntax requires an imported helper but module'tslib'cannot...
randomValue ='Mateo';if(typeofrandomValue ==="string") {console.log((randomValueasstring).toUpperCase());//* Returns MATEO to the console.}else{console.log("Error - A string was expected here.");//* Returns an error message.}
This often results in error messages such as: Copy Property 'message' does not exist on type 'unknown'. Property 'name' does not exist on type 'unknown'. Property 'stack' does not exist on type 'unknown'. To get around this, you can specifically add runtime checks to ensure that ...
function error(message: string): never { throw new Error(message); } function infiniteLoop(): never { while (true) {} } 在TypeScript 中,可以利用 never 类型的特性来实现全面性检查,具体示例如下: type Foo = string | number; function controlFlowAnalysisWithNever(foo: Foo) { ...
Related error spans Part of the goal of providing a good error message is also guiding a user towards a way to fix the error, or providing a way to intuit why the error message was given in the first place. Much of the time, there can be a lot of information or multiple reasons an...