The “Object is possibly null” error occurs when the Typescript compiler cannot guarantee that a variable is not null or undefined when accessing its properties or methods. This is because, by default, Typescript allows variables to be null or undefined unless explicitly specified otherwise. For ...
A 'this'-based type guard is not compatible with a parameter-based type guard.2520 错误 Duplicate identifier '{0}'. Compiler uses declaration '{1}' to support async functions. 标识符“{0}”重复。编译器使用“{1}”声明来支持异步函数。2521 错误 Expression resolves to variable declaration '{0...
1188 错误 Only a single variable declaration is allowed in a 'for...of' statement. "for...of" 语句中只允许单个变量声明。1189 错误 The variable declaration of a 'for...in' statement cannot have an initializer. "for...in" 语句的变量声明不能有初始化表达式。1190 错误 The variable declarati...
1188 错误 Only a single variable declaration is allowed in a 'for...of' statement. "for...of" 语句中只允许单个变量声明。 1189 错误 The variable declaration of a 'for...in' statement cannot have an initializer. "for...in" 语句的变量声明不能有初始化表达式。 1190 错误 The variable decla...
myvariable.subproperty?.value和myvariable.subproperty!.value有什么区别? 、 value之间的区别是:如果子属性为null,则两者似乎都执行,从而传递一个空值。我知道断言操作符的一般含义,只是不确定当您这样链接调用属性时意味着什么。谢谢! 浏览2提问于2022-01-06得票数 0 回答已采纳 1回答 使用Typescript和Auth0设...
对象可能为"null“- TypeScript链接程序出错 问题:对象可能为"null" - TypeScript链接程序出错 回答:在TypeScript中,当我们声明一个变量时,它的类型可以是任意类型,包括对象类型。然而,有时候我们可能会遇到一个问题,即对象可能为"null",这可能导致程序出错。 为了解决这个问题,我们可以使用可选链操作符(Optio...
现在,每当我们使用.getNextLine()返回的值时,TypeScript 强制我们考虑两种可能性:字符串和null,例如: functioncountComments(is: InputStream) {letcommentCount =0;while(true) {constline = is.getNextLine();// @ts-expect-error: Object is possibly 'null'.(2531)if(line.startsWith('#')) {// (A)...
temporaryWork *=2;// forgot to assign to 'result'}console.log(result);// error: Variable 'result' is used before being assigned. Unfortunately, there are some places where this analysis doesn’t work. For example, if the variable is accessed in a separate function, the type system doesn...
varname:string;// cannot be null and undefined.name =undefined;// Error: [ts] Type 'undefined' is not assignable to type 'string'.name =null;// Error: [ts] Type 'null' is not assignable to type 'string'.console.log(name);// Error: [ts] Variable 'address' is used before being ...
foo=null//Type 'null' is not assignable to type 'number'. console.log(foo); Data Types The Undefined & null also have corresponding types named after them. The Data Type of undefined is undefined and that of null is null. We can create a variable of type undefined or null byannotating...