TypeScript 里,undefined和null两者有各自的类型分别为undefined和null。 默认情况下null和undefined是所有类型的子类型。 就是说你可以把null和undefined赋值给number类型的变量。然而,如果你指定了--strictNullChecks标记,null和undefined只能赋值给void和它们各自的类型。 2.12 object, Object 和 {} 类型 1.object 类型...
let variable: any = 'a string'; variable = 5; variable = false; variable.someRandomMethod(); /* 行吧, 也许运行的时候 someRandomMethod 是存在的 */ Void (空值) void表示没有任何类型。它通常用作没有返回值的函数的返回类型。 function sayMyName(name: string): void { console.log(name); }...
你可以使用 juggle-check,它检查 null 和 undefined,或者使用 strict-check,它返回true设置为null的值,并且不会评估true未定义的变量。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 //juggle if (x == null) { } var a: number; var b: number = null; function check(x, name) { if (x =...
) -i, --ignore-files [string[]] 忽略指定文件, eg: --ignore-files "demo1/*.ts" --ignore-files "demo2/foo.ts" (默认值: 否) --ignore-catch [boolean] ignore type any for (try-)catch clause variable (default: false) -u, --ignore-unread [boolean] 允许写入具有Any类型的变量 (...
When the property name is completed, the missing comma is automatically inserted., image For more information, see the implementation here. Inline Variable Refactoring TypeScript 5.2 now has a refactoring to inline the contents of a variable to all usage sites. A variable called 'path' ...
var b: number = null; function check(x, name) { if (x == null) { console.log(name + ' == null'); } if (x === null) { console.log(name + ' === null'); } if (typeof x === 'undefined') { console.log(name + ' is undefined'); ...
如果一个interface没有在声明中输出,tsc 不会去内联查询这个类型,而是抛出一个异常(例如:TS4023: Exported variable has or is using name from external module but cannot be named.)。 如果一个type没有在声明中输出,tsc 会在依赖中内联寻找这个类型的定义。
variable, find who’s using a given function, and automate refactorings and fixes to common problems. TypeScript even provides this for JavaScript users (and can also type-check JavaScript code typed with JSDoc), so if you’ve used editors like Visual Studio or Visual Studio Code on a.js...
Declare a variable:let x: number; Do some complicated logic to possibly assign it If it wasn't assigned, provide a default value. Currently, we can't compile this function. We get an error for!xsayingVariable 'x' is used before being assigned. ...
Trying to attach a non-null assertion using the concrete union suggested above does not seem to be working. I'm trying to write a generic "normalize" function that will be executed on user input only if that input is defined: type Defined = string|number|boolean|symbol|object|null; interfa...