inflearn logo
강의

강의

N
챌린지

챌린지

멘토링

멘토링

N
클립

클립

로드맵

로드맵

지식공유

[리뉴얼] 타입스크립트 올인원 : Part1. 기본 문법편

never 타입과 느낌표(non-null assertion)

안녕하세요.

해결된 질문

841

Milkyway

작성한 질문수 35

0

안녕하세요. 궁금한게 있어서 질문 드립니다.

수업 도중에 빈 배열 위에 드래그 후 마우스를 올렸을때 강좌에서는 const array: never 라는 팝업이 뜨는데 저는 빈 배열을 드래그 했을때나 드래그 하지 않았을 때 아무 것도 뜨지 않으며 array는 any가 떠서 어떻게 하면 확인할수 있는지 질문 드립니다.

IDE는 웹스톰 사용하고 있습니다.

typescript

답변 1

1

제로초(조현영)

일단 array에 any[]나 never[]가 뜨는 게 맞고요. tsconfig.json에서 strict: true 넣으시면 됩니다.

0

Milkyway

답변 감사합니다 

기존에 tsconfig.json파일의 "strict" 프로퍼티가 true로 돼 있는데도 any만 뜨네요ㅠㅠ 

혹시 몰라서 basic 디렉토리에 sample.ts 파일을 생성 후 저 코드만 넣었는데도 any[] 만 뜹니다. 확인 부탁들도 될까요? 감사합니다.
https://github.com/rae-han/learn-typescript/tree/main/all-in-one

```

{
"compilerOptions": {
/* Visit https://aka.ms/tsconfig to read more about this file */

/* Projects */
// "incremental": true, /* Save .tsbuildinfo files to allow for incremental compilation of projects. */
// "composite": true, /* Enable constraints that allow a TypeScript project to be used with project references. */
// "tsBuildInfoFile": "./.tsbuildinfo", /* Specify the path to .tsbuildinfo incremental compilation file. */
// "disableSourceOfProjectReferenceRedirect": true, /* Disable preferring source files instead of declaration files when referencing composite projects. */
// "disableSolutionSearching": true, /* Opt a project out of multi-project reference checking when editing. */
// "disableReferencedProjectLoad": true, /* Reduce the number of projects loaded automatically by TypeScript. */

/* Language and Environment */
"target": "es2016", /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
// "lib": [], /* Specify a set of bundled library declaration files that describe the target runtime environment. */
// "jsx": "preserve", /* Specify what JSX code is generated. */
// "experimentalDecorators": true, /* Enable experimental support for TC39 stage 2 draft decorators. */
// "emitDecoratorMetadata": true, /* Emit design-type metadata for decorated declarations in source files. */
// "jsxFactory": "", /* Specify the JSX factory function used when targeting React JSX emit, e.g. 'React.createElement' or 'h'. */
// "jsxFragmentFactory": "", /* Specify the JSX Fragment reference used for fragments when targeting React JSX emit e.g. 'React.Fragment' or 'Fragment'. */
// "jsxImportSource": "", /* Specify module specifier used to import the JSX factory functions when using 'jsx: react-jsx*'. */
// "reactNamespace": "", /* Specify the object invoked for 'createElement'. This only applies when targeting 'react' JSX emit. */
// "noLib": true, /* Disable including any library files, including the default lib.d.ts. */
// "useDefineForClassFields": true, /* Emit ECMAScript-standard-compliant class fields. */
// "moduleDetection": "auto", /* Control what method is used to detect module-format JS files. */

/* Modules */
"module": "CommonJS", /* Specify what module code is generated. */
// "rootDir": "./", /* Specify the root folder within your source files. */
// "moduleResolution": "node", /* Specify how TypeScript looks up a file from a given module specifier. */
// "baseUrl": "./", /* Specify the base directory to resolve non-relative module names. */
// "paths": {}, /* Specify a set of entries that re-map imports to additional lookup locations. */
// "rootDirs": [], /* Allow multiple folders to be treated as one when resolving modules. */
// "typeRoots": [], /* Specify multiple folders that act like './node_modules/@types'. */
// "types": [], /* Specify type package names to be included without being referenced in a source file. */
// "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */
// "moduleSuffixes": [], /* List of file name suffixes to search when resolving a module. */
// "resolveJsonModule": true, /* Enable importing .json files. */
// "noResolve": true, /* Disallow 'import's, 'require's or '<reference>'s from expanding the number of files TypeScript should add to a project. */

/* JavaScript Support */
"allowJs": true, /* Allow JavaScript files to be a part of your program. Use the 'checkJS' option to get errors from these files. */
// "checkJs": true, /* Enable error reporting in type-checked JavaScript files. */
// "maxNodeModuleJsDepth": 1, /* Specify the maximum folder depth used for checking JavaScript files from 'node_modules'. Only applicable with 'allowJs'. */

/* Emit */
// "declaration": true, /* Generate .d.ts files from TypeScript and JavaScript files in your project. */
// "declarationMap": true, /* Create sourcemaps for d.ts files. */
// "emitDeclarationOnly": true, /* Only output d.ts files and not JavaScript files. */
// "sourceMap": true, /* Create source map files for emitted JavaScript files. */
// "outFile": "./", /* Specify a file that bundles all outputs into one JavaScript file. If 'declaration' is true, also designates a file that bundles all .d.ts output. */
// "outDir": "./", /* Specify an output folder for all emitted files. */
// "removeComments": true, /* Disable emitting comments. */
// "noEmit": true, /* Disable emitting files from a compilation. */
// "importHelpers": true, /* Allow importing helper functions from tslib once per project, instead of including them per-file. */
// "importsNotUsedAsValues": "remove", /* Specify emit/checking behavior for imports that are only used for types. */
// "downlevelIteration": true, /* Emit more compliant, but verbose and less performant JavaScript for iteration. */
// "sourceRoot": "", /* Specify the root path for debuggers to find the reference source code. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Include sourcemap files inside the emitted JavaScript. */
// "inlineSources": true, /* Include source code in the sourcemaps inside the emitted JavaScript. */
// "emitBOM": true, /* Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files. */
// "newLine": "crlf", /* Set the newline character for emitting files. */
// "stripInternal": true, /* Disable emitting declarations that have '@internal' in their JSDoc comments. */
// "noEmitHelpers": true, /* Disable generating custom helper functions like '__extends' in compiled output. */
// "noEmitOnError": true, /* Disable emitting files if any type checking errors are reported. */
// "preserveConstEnums": true, /* Disable erasing 'const enum' declarations in generated code. */
// "declarationDir": "./", /* Specify the output directory for generated declaration files. */
// "preserveValueImports": true, /* Preserve unused imported values in the JavaScript output that would otherwise be removed. */

/* Interop Constraints */
// "isolatedModules": true, /* Ensure that each file can be safely transpiled without relying on other imports. */
// "allowSyntheticDefaultImports": true, /* Allow 'import x from y' when a module doesn't have a default export. */
"esModuleInterop": true, /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
// "preserveSymlinks": true, /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */
"forceConsistentCasingInFileNames": true, /* Ensure that casing is correct in imports. */
// 윈도우와 맥, 리눅스 간의 파일 모듈 시스템이 대한 차이(윈도우는 대소문자 구별 X)

/* Type Checking */
"strict": true, /* Enable all strict type-checking options. */
// "noImplicitAny": true, /* Enable error reporting for expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* When type checking, take into account 'null' and 'undefined'. */
// "strictFunctionTypes": true, /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */
// "strictBindCallApply": true, /* Check that the arguments for 'bind', 'call', and 'apply' methods match the original function. */
// "strictPropertyInitialization": true, /* Check for class properties that are declared but not set in the constructor. */
// "noImplicitThis": true, /* Enable error reporting when 'this' is given the type 'any'. */
// "useUnknownInCatchVariables": true, /* Default catch clause variables as 'unknown' instead of 'any'. */
// "alwaysStrict": true, /* Ensure 'use strict' is always emitted. */
// "noUnusedLocals": true, /* Enable error reporting when local variables aren't read. */
// "noUnusedParameters": true, /* Raise an error when a function parameter isn't read. */
// "exactOptionalPropertyTypes": true, /* Interpret optional property types as written, rather than adding 'undefined'. */
// "noImplicitReturns": true, /* Enable error reporting for codepaths that do not explicitly return in a function. */
// "noFallthroughCasesInSwitch": true, /* Enable error reporting for fallthrough cases in switch statements. */
// "noUncheckedIndexedAccess": true, /* Add 'undefined' to a type when accessed using an index. */
// "noImplicitOverride": true, /* Ensure overriding members in derived classes are marked with an override modifier. */
// "noPropertyAccessFromIndexSignature": true, /* Enforces using indexed accessors for keys declared using an indexed type. */
// "allowUnusedLabels": true, /* Disable error reporting for unused labels. */
// "allowUnreachableCode": true, /* Disable error reporting for unreachable code. */

/* Completeness */
// "skipDefaultLibCheck": true, /* Skip type checking .d.ts files that are included with TypeScript. */
"skipLibCheck": true /* Skip type checking all .d.ts files. */
// 라이브러리 타입 체크
}
}

```

0

제로초(조현영)

아, 추가로 noImplicitAny가 false여야 never로 뜹니다.

정확한 조건은 !noImplicitAny && strictNullChecks 입니다.

0

Milkyway

감사합니다!! 이건 질문 올리기 전에 제가 한번 tsconfig를 읽었어야 하는 문제였네요ㅠㅠ 급한 마음에 질문부터 올렸는데 친절히 알려주셔서 감사합니다!!

데코레이터가 현재도 자주 쓰이는 문법인가요?

0

81

2

유틸리티 타입 실제로 구현은 못해도 하나씩 외우면 실무할 때 지장 없겠죠?

0

66

1

매핑 타입은 type에서밖에 안된다고 하네요?

0

65

2

자바에서의 오버로딩과 같은 개념이라고 생각해도 되나요?

0

69

2

filter 함수 반환 타입 네로잉 질문

0

74

2

map<U>(callbackfn: ....) 할때 U는 왜 여기 있는거에요??

0

49

2

ts 컴파일을 위한 type 라벨링 부분

0

46

1

concat 함수 타입 구현 중 질문 있습니다!

0

100

2

filter 메소드 질문

0

53

1

forEach 제네릭 관련 문의

0

60

1

타입 추론 시 가장 넓은 범위로 추론이 되는 건가요?

0

166

1

enum이 javascript로 트랜스파일링될때 사라진다하셨는데요

0

207

1

함수 파라미터 타입 정의 시 ...args: any[]와 ...args: any 의 차이

0

223

1

Flat type에서 ReadonlyArray 타입을 사용하는 이유?

0

157

1

bind type 질문

1

149

1

Lowercase type 관련 질문

0

152

1

key-value 타입 자동추론 질문드립니다

0

266

1

타입스크립트 교과서, p131

0

266

1

타입스크립트 교과서 p122 forEach 메서드 질문

0

233

1

타입스크립트 교과서 p116 , 코드에러남

1

269

1

타입스크립트 교과서 p112 , 코드가 안읽힙니다..

0

267

1

타입스크립트 교과서 p83

1

184

1

타입스크립트교과서 p39 쪽 코드가 이해가 안되요

1

227

1

class 에서 ts의 private vs js의 private field( # )

0

339

1