function f(this: void) { // make sure `this` is unusable in this standalone function } 给上面的例子加一些类型,让类型更加清晰且易于重用: interface Card { suit: string; card: number; } interface Deck { suits: string[]; cards: number[]; createCardPicker(this: Deck): () => Card; }...
functionloggedMethod(originalMethod:any,context:ClassMethodDecoratorContext){constmethodName=String(context.name);functionreplacementMethod(this:any,...args:any[]){console.log(`LOG: Entering method '${methodName}'.`)constresult=originalMethod.call(this,...args);console.log(`LOG: Exiting method '${...
上面的设置使得 TypeScript 对于语句import * as foo from "./foo";,会搜索以下脚本./foo.ios.ts、./foo.native.ts和./foo.ts。 29. newLine newLine设置换行符为CRLF(Windows)还是LF(Linux)。 30. noEmit noEmit设置是否产生编译结果。如果不生成,TypeScript 编译就纯粹作为类型检查了。 31. noEmitHelpers...
return name; } */// "noImplicitAny": true, /*为隐含的'any'类型的表达式和声明启用错误报告*/// "strictNullChecks": true, /*在进行类型检查时,请考虑'null'和'undefined'——null类型检测,const teacher: string = null;会报错*/// "strictFunctionTypes": true, /*分配函数时,请检查以确保参数和...
const emittedFilesList: string[] = compilerOptions.listEmittedFiles ? [] : undefined; const emitterDiagnostics = createDiagnosticCollection(); const newLine = host.getNewLine(); const writer = createTextWriter(newLine); const sourceMap = createSourceMapWriter(host, writer); ...
function f1(obj: Record<string, unknown>, key: string) { if (typeof obj[key] === "string") { // Now okay, previously was error obj[key].toUpperCase(); } } In the above, neither obj nor key are ever mutated, so TypeScript can narrow the type of obj[key] to string after th...
When calling generic functions, TypeScript is able to infer type arguments from whatever you pass in. Copy functiondoSomething<T>(arg: T){// ...}// We can explicitly say that 'T' should be 'string'.doSomething<string>("hello!");// We can also just let the type of 'T' get infe...
this.id = String; this.name = String; this.age = Number; } } const user = { id: 'user_id_01', name: 'Jade', age: 18 }; 我们可以看到,由 ObjectType 定义的 User Schema 在运行时也得到了保留,因此我们可以基于这些信息,实现在运行时的 Validation 和 Introspection 功能。
A Common Routes File in TypeScript In thecommonfolder, let’s create thecommon.routes.config.tsfile to look like the following: importexpressfrom'express';exportclassCommonRoutesConfig{app: express.Application;name:string;constructor(app: express.Application, name:string) {this.app= app;this.name...
There are no type annotations in this program, but TypeScript’s type checker is still able to spot the problem: letcity='new york city';console.log(city.toUppercase());// ~~~ Property 'toUppercase' does not exist on type// 'string'. Did you mean 'toUpperCase'? You didn’t...