「TypeScript」的原始类型包括:「boolean、number、string、void、undefined、null、symbol、bigint。」 需要注意的是,number是类型,而Number是构造函数。 当函数没有返回值时,返回类型就是void。只有null和undefined可以赋给void。 默认情况下null和undefined是所
Type 'undefined' is not assignable to type 'number'. 7 ataolaFI = function (arr: number[], num: number) { ~~~ Found 1 error. 这里的话少考虑一种情况就是,要是找不到呢?后面改正的代码是 代码语言:javascript 代码运行次数:0 运行 AI代码解释 //一个基于Typescript,数字数组索引查找的实现 int...
functionhello(who:string):string{return'Hello, '+who;}functionhelloStartingWith(letter:string):string{constpeople=['Alice','Bob','Carol'];constperson=people.find(name=>name.startsWith(letter));returnhello(person);// This is the error:// Argument of type 'string | undefined' is not assigna...
as well asIterator.prototype, as actual values in JavaScript. This is a bit awkward since TypeScript already defines its own thing calledIteratorpurely for type-checking. So due to this unfortunate name clash, TypeScript needs to introduce a separate type to describe these native/built-in iterab...
maybeString != undefined && typeof checker.maybeString != "string") || !sanitizeBar(checker.bar) ) { return false; } return true; } function sanitizeBar(checker: any) { if (!sanitizenumberArray(checker.numbers)) { return false; } return true; } function sanitizenumberArray(checker: any...
if (otherName !== undefined) { this.name = otherName; } } err() { this.name = "not ok"; //Cannot assign to 'name' because it is a read-only property. } } const g = new Greeter(); g.name = "also not ok"; //Cannot assign to 'name' because it is a read-only property...
The if(pet.swim) type guard would eleminte the undefined from the result type in the body of the if statement, and pet.swim() would be allowed, too. The same would be the case for if(pet.fly). This less restictive type checking does not cause any runtime errors, and more ...
In this code example; dataSet[index] reports the same error as above even though in the check before we are checking for undefined and null states? VS Code version: Code 1.52.0 (940b5f4, 2020-12-10T22:46:53.673Z) OS version: Darwin x64 20.1.0 System Info Extensions (33) A/B ...
/* Enable all strict type-checking options. */"esModuleInterop": true, /* Enables emit interoperability between CommonJS and ES */"skipLibCheck": true, /* Skip type checking of declaration files. */"forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the ...
One of TypeScript’s core principles is that type checking focuses on the shape that values have...