express.json() is an unknown property - javascript

Typescript doesn't recognize the express.json() function although many tutorials state this code should compile as it is.
Is there something I have done wrong?
Example tutorial where this is stated to be working: https://auth0.com/blog/node-js-and-typescript-tutorial-build-a-crud-api/#test-the-express-api-endpoints
Moreover I know this works in normal Node.js but have never tried it in Typescript.
const version = require('../package.json').version;
import express from 'express';
console.log("Application is running on version " + version);
const app = express();
app.use(express.json());
app.listen(7777);
Compiler output:
app.ts:10:17 - error TS2339: Property 'json' does not exist on type 'Express'.
10 app.use(express.json());
~~~~
Found 1 error.
npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! test#1.0.0 start: `tsc --outDir dist && node dist/app.js`
npm ERR! Exit status 2
npm ERR!
npm ERR! Failed at the test#1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\name\AppData\Roaming\npm-cache\_logs\2021-07-15T14_34_22_294Z-debug.log
tsconfig.json
{
"compilerOptions": {
/* Visit https://aka.ms/tsconfig.json to read more about this file */
/* Basic Options */
// "incremental": true, /* Enable incremental compilation */
"target": "es5", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', 'ES2021', or 'ESNEXT'. */
"module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
// "lib": [], /* Specify library files to be included in the compilation. */
// "allowJs": true, /* Allow javascript files to be compiled. */
// "checkJs": true, /* Report errors in .js files. */
// "jsx": "preserve", /* Specify JSX code generation: 'preserve', 'react-native', 'react', 'react-jsx' or 'react-jsxdev'. */
// "declaration": true, /* Generates corresponding '.d.ts' file. */
// "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
// "outDir": "./", /* Redirect output structure to the directory. */
// "rootDir": "./", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "composite": true, /* Enable project compilation */
// "tsBuildInfoFile": "./", /* Specify file to store incremental compilation information */
// "removeComments": true, /* Do not emit comments to output. */
// "noEmit": true, /* Do not emit outputs. */
// "importHelpers": true, /* Import emit helpers from 'tslib'. */
// "downlevelIteration": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
// "isolatedModules": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
/* Strict Type-Checking Options */
"strict": true, /* Enable all strict type-checking options. */
// "noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* Enable strict null checks. */
// "strictFunctionTypes": true, /* Enable strict checking of function types. */
// "strictBindCallApply": true, /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
// "strictPropertyInitialization": true, /* Enable strict checking of property initialization in classes. */
// "noImplicitThis": true, /* Raise error on 'this' expressions with an implied 'any' type. */
// "alwaysStrict": true, /* Parse in strict mode and emit "use strict" for each source file. */
/* Additional Checks */
// "noUnusedLocals": true, /* Report errors on unused locals. */
// "noUnusedParameters": true, /* Report errors on unused parameters. */
// "noImplicitReturns": true, /* Report error when not all code paths in function return a value. */
// "noFallthroughCasesInSwitch": true, /* Report errors for fallthrough cases in switch statement. */
// "noUncheckedIndexedAccess": true, /* Include 'undefined' in index signature results */
// "noImplicitOverride": true, /* Ensure overriding members in derived classes are marked with an 'override' modifier. */
// "noPropertyAccessFromIndexSignature": true, /* Require undeclared properties from index signatures to use element accesses. */
/* Module Resolution Options */
// "moduleResolution": "node", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
// "baseUrl": "./", /* Base directory to resolve non-absolute module names. */
// "paths": {}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
// "rootDirs": [], /* List of root folders whose combined content represents the structure of the project at runtime. */
// "typeRoots": [], /* List of folders to include type definitions from. */
// "types": [], /* Type declaration files to be included in compilation. */
// "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
"esModuleInterop": true, /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
// "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */
/* Source Map Options */
// "sourceRoot": "", /* Specify the location where debugger should locate TypeScript files instead of source locations. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Emit a single file with source maps instead of having a separate file. */
// "inlineSources": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
/* Experimental Options */
// "experimentalDecorators": true, /* Enables experimental support for ES7 decorators. */
// "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
/* Advanced Options */
"skipLibCheck": true, /* Skip type checking of declaration files. */
"forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the same file. */
}
}

Check the version of your devDependencies.
It should look something like that.
"devDependencies": {
"#types/express": "^4.17.12",
}

The problem could be identified in the package.json file.
Somehow the version of the #types/express package was defined with the version "github:types/express" which seems not to be the most current.
The fix was to update the package.json file from
{
"name": "test",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"start": "tsc --outDir dist && node dist/app.js",
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"#types/body-parser": "^1.19.1",
"body-parser": "^1.19.0",
"express": "^4.17.1",
"tslint": "^6.1.3"
},
"devDependencies": {
"#types/express": "github:types/express",
"#types/node": "^16.3.2",
"ts-node": "^10.1.0",
"ts-node-dev": "^1.1.8",
"typescript": "^4.3.5"
}
}
to (only the version of "#types/express" has been changed)
{
"name": "test",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"start": "tsc --outDir dist && node dist/app.js",
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"#types/body-parser": "^1.19.1",
"body-parser": "^1.19.0",
"express": "^4.17.1",
"tslint": "^6.1.3"
},
"devDependencies": {
"#types/express": "^4.17.12",
"#types/node": "^16.3.2",
"ts-node": "^10.1.0",
"ts-node-dev": "^1.1.8",
"typescript": "^4.3.5"
}
}

changing from import express from 'express' to import * as express from 'express' did it for me

Related

Package do not import correctly in project

I recently created a Typescript Package that I would like to test in an app before publishing on NPM.
The entry file (index.ts) looks like this =>
import Builder from './core/builder';
export default Builder;
Basically, there is many files, but I want the user to just use a "static" class Builder that I export in the index. so the user can just do import Builder from 'builderts'
My package.json folder is the following
"name": "builderts",
"main": "./dist/builderts.js",
"types": "./dist/builderts.d.ts",
"files": [
"dist/*"
],
"scripts": {
"preversion" : "npm run lint",
"prepare": "npm run build",
"prepublishOnly": "npm test && npm run lint",
"version" : "npm run format && git add -A src",
"postversion" : "git push && git push --tags",
"build": "tsc",
"watch": "tsc-watch",
"format": "prettier --write \"src/**/*.ts\" \"src/**/*.js\"",
"lint": "eslint tsconfig.json"
},
and my tsconfig.json
{
"compilerOptions": {
"target": "es6", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
"module": "amd", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
"declaration": true, /* Generates corresponding '.d.ts' file. */
"declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
"sourceMap": true, /* Generates corresponding '.map' file. */
"outFile":"./dist/builderts.js", /* Concatenate and emit output to single file. */
"outDir": "dist", /* Redirect output structure to the directory. */
"strict": true, /* Enable all strict type-checking options. */
"esModuleInterop": true, /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
"forceConsistentCasingInFileNames": true /* Disallow inconsistently-cased references to the same file. */
},
"include": ["src"],
"exclude": ["node_modules", "dist"]
}
The problem I face is, I tried to create a small test project and install the module using
npm install absolute/path
it install correctly, but when I try to import the package using
import Builder from 'builderts';
I do not have neither autocompletion, and I have an error saying
File 'D:/User/Local/gitRepo/builderts/dist/builderts.d.ts' is not a module.
I do not quite understand what I am missing in the process.
Looks to me that you need to update the types in package.json
You stated above that the file name was index.ts, have you considered updating package.json ? :
{
...
"types": "./dist/index.ts",
...
}

Adding tsconfig exclude causes "Cannot write file" errors? in VSCode

If I add this exclude block to my tsconfig.json file:
"exclude": ["angular-package-format-workspace"]
The following errors appear in VSCode. They disappear if I remove the exclude block (Also the exclude block has the desired affect - so just curious why VSCode is painting the errors):
SON schema for the TypeScript compiler's configuration file
Cannot write file '/home/ole/Github/slice/target/dist/index.d.ts' because it would overwrite input file.ts
Cannot write file '/home/ole/Github/slice/target/dist/index.d.ts' because it would overwrite input file.ts
Cannot write file '/home/ole/Github/slice/target/dist/index.d.ts' because it would overwrite input file.ts
This is my tsconfig.json file:
{
"compilerOptions": {
"target": "es5", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
"module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
"lib": ["es2017"], /* Specify library files to be included in the compilation. */
"declaration": true, /* Generates corresponding '.d.ts' file. */
"sourceMap": true, /* Generates corresponding '.map' file. */
"outDir": "./target", /* Redirect output structure to the directory. */
"strict": true, /* Enable all strict type-checking options. */
"strictNullChecks": false, /* Enable strict null checks. */
"baseUrl": "./", /* Base directory to resolve non-absolute module names. */
"paths": {
"#fs/*": ["./src/*"],
"#test/*": ["./test/*"]
}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
"plugins": [
{ "transform": "typescript-transform-paths" },
{ "transform": "typescript-transform-paths", "afterDeclarations": true }
],
"rootDirs": ["./src/"], /* List of root folders whose combined content represents the structure of the project at runtime. */
"esModuleInterop": true, /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
"experimentalDecorators": true /* Enables experimental support for ES7 decorators. */
},
"exclude": ["angular-package-format-workspace"]
}
Try adding the block, saving, then restarting Visual Studio Code.
Visual Studio Code holds open files when it is running, and this can conflict with other programs trying to read/write to them.

Create Readable JS from Typescript

I want my compiled JS code to be readable (similar as if I had written it), so it's easier to debug but the typescript compiler makes several changes which I'm hoping I can turn off.
For example:
When I compile my typescript it changes all the import names eg.
import AWS from 'aws-sdk' => const aws_sdk_1 = __importDefault(require("aws-sdk"));
rather than const aws-sdk = require('aws-sdk')
Additionally, it removed all line spacing, which I included to make it more readable and break it up.
Is there any way to change these settings?
tsconfig.json
{
"compilerOptions": {
/* Basic Options */
// "incremental": true, /* Enable incremental compilation */
"target": "es2017",
/* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
"module": "commonjs",
/* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
// "lib": [], /* Specify library files to be included in the compilation. */
"allowJs": true,
/* Allow javascript files to be compiled. */
"checkJs": true,
/* Report errors in .js files. */
// "jsx": "preserve", /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
// "declaration": true, /* Generates corresponding '.d.ts' file. */
// "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
"outDir": "./dist",
/* Redirect output structure to the directory. */
// "rootDir": "./", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "composite": true, /* Enable project compilation */
// "tsBuildInfoFile": "./", /* Specify file to store incremental compilation information */
// "removeComments": true, /* Do not emit comments to output. */
// "noEmit": true, /* Do not emit outputs. */
// "importHelpers": true, /* Import emit helpers from 'tslib'. */
// "downlevelIteration": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
// "isolatedModules": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
/* Strict Type-Checking Options */
"strict": true,
/* Enable all strict type-checking options. */
// "noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* Enable strict null checks. */
// "strictFunctionTypes": true, /* Enable strict checking of function types. */
// "strictBindCallApply": true, /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
// "strictPropertyInitialization": true, /* Enable strict checking of property initialization in classes. */
// "noImplicitThis": true, /* Raise error on 'this' expressions with an implied 'any' type. */
// "alwaysStrict": false, /* Parse in strict mode and emit "use strict" for each source file. */
/* Additional Checks */
// "noUnusedLocals": true, /* Report errors on unused locals. */
// "noUnusedParameters": true, /* Report errors on unused parameters. */
// "noImplicitReturns": true, /* Report error when not all code paths in function return a value. */
// "noFallthroughCasesInSwitch": true, /* Report errors for fallthrough cases in switch statement. */
/* Module Resolution Options */
"moduleResolution": "node",
/* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
// "baseUrl": "./", /* Base directory to resolve non-absolute module names. */
// "paths": {}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
// "rootDirs": [], /* List of root folders whose combined content represents the structure of the project at runtime. */
// "typeRoots": [], /* List of folders to include type definitions from. */
// "types": [], /* Type declaration files to be included in compilation. */
// "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
"esModuleInterop": true,
/* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
"allowUmdGlobalAccess": true,
/* Allow accessing UMD globals from modules. */
/* Source Map Options */
// "sourceRoot": "", /* Specify the location where debugger should locate TypeScript files instead of source locations. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Emit a single file with source maps instead of having a separate file. */
// "inlineSources": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
/* Experimental Options */
"experimentalDecorators": true,
/* Enables experimental support for ES7 decorators. */
// "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
}
}
If the problem in debugging is the only reason you want readable JS. Then you can debug your ts file (readable) in chrome using this command
node --inspect -r ts-node/register <your-ts-file.ts>
For the above command, you will first have to install ts-node.
npm install --save ts-node
You cannot preserve whitespace. The processing required by TS compiler, which is dependent on the tsconfig settings, and could dramatically change the output, does not allow for trying to keep any formatting intact.
The target and module system you have will change the output JS, especially imports. TS will try to handle all the scenarios, even if you wouldn't normally.
You can turn off the __importDefault helper functions however by using
esModuleInterop: false
You should treat the generated js as a binary. It is a built output, and you shouldn't care about it's format. You wouldn't look inside a DLL and care what it looked like. The only time you will ever need to care would be if you were moving away from TS, and if that were the case, processing the files to simply remove the TS annotations would be more easy than trying to make the transpiled source look exactly like you want it.
For debugging, source maps are critical. Output them, and debug your TS, not the generated JS.

Protractor Typescript Problem converting ts to js file in tsConfig file. How do I fix this?

I tried to convert the ts to a js file in I thought I had set up the tsconfig file correct correctly.
However when I type tsc expecting my sample file to convert from ts to js I got another ts file.
What did I do wrong
You can watch I what i did by clicking here (this was a personal video tutorial I was creating!)
My question is simple:
1.What did I do wrong?
2.How do I fix it?
This is my tsconfig.json code
{
"compilerOptions": {
/* Basic Options */
"target": "es6", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
"module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
"moduleResolution": "node",
"inlineSourceMap": true,
"declaration": false,
"noImplicitAny": false,
"sourceMap": false,
"removeComments": false,
// "lib": [], /* Specify library files to be included in the compilation. */
// "allowJs": true, /* Allow javascript files to be compiled. */
// "checkJs": true, /* Report errors in .js files. */
// "jsx": "preserve", /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
// "declaration": true, /* Generates corresponding '.d.ts' file. */
// "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
"outDir": "JSFiles", /* Redirect output structure to the directory. */
// "rootDir": "./", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "composite": true, /* Enable project compilation */
// "removeComments": true, /* Do not emit comments to output. */
// "noEmit": true, /* Do not emit outputs. */
// "importHelpers": true, /* Import emit helpers from 'tslib'. */
// "downlevelIteration": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
// "isolatedModules": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
/* Strict Type-Checking Options */
/* Enable all strict type-checking options. */
// "noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* Enable strict null checks. */
// "strictFunctionTypes": true, /* Enable strict checking of function types. */
// "strictBindCallApply": true, /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
// "strictPropertyInitialization": true, /* Enable strict checking of property initialization in classes. */
// "noImplicitThis": true, /* Raise error on 'this' expressions with an implied 'any' type. */
// "alwaysStrict": true, /* Parse in strict mode and emit "use strict" for each source file. */
/* Additional Checks */
// "noUnusedLocals": true, /* Report errors on unused locals. */
// "noUnusedParameters": true, /* Report errors on unused parameters. */
// "noImplicitReturns": true, /* Report error when not all code paths in function return a value. */
// "noFallthroughCasesInSwitch": true, /* Report errors for fallthrough cases in switch statement. */
/* Module Resolution Options */
// "moduleResolution": "node", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
// "baseUrl": "./", /* Base directory to resolve non-absolute module names. */
// "paths": {}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
// "rootDirs": [], /* List of root folders whose combined content represents the structure of the project at runtime. */
// "typeRoots": [], /* List of folders to include type definitions from. */
// "types": [], /* Type declaration files to be included in compilation. */
// "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
"esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
/* Source Map Options */
// "sourceRoot": "", /* Specify the location where debugger should locate TypeScript files instead of source locations. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Emit a single file with source maps instead of having a separate file. */
// "inlineSources": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
/* Experimental Options */
// "experimentalDecorators": true, /* Enables experimental support for ES7 decorators. */
// "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
},
"exclude": [
"node_modules"
]
}
Can you try this tsconfig file -
{
"compilerOptions": {
"module": "commonjs",
"target": "es6",
"moduleResolution": "node",
"sourceMap": false,
"declaration": false,
"removeComments": false,
"noImplicitAny": false,
"skipLibCheck": true,
"outDir": "JSFiles",
"typeRoots": [ "./node_modules/#types" ],
"types": ["node"]
},
"exclude": [
"node_modules",
"typescript"
]
}

How do I target ES2018 in TypeScript?

I am targeting ES2018 and do not care about ES3 or ES5. From my tsconfig.json: "target": "ES2018". tsc complains:
An async function or method in ES5/ES3 requires the 'Promise' constructor. Make
sure you have a declaration for the 'Promise' constructor or include 'ES2015' in your --lib option.
I know I could add "lib": ["es2015"] to add libraries to the compilation but I don't need those libraries, I am targeting ES2018.
How do I target ES2018 in TypeScript?
Here is my tsconfig.json:
{
"compilerOptions": {
/* Basic Options */
"target": "ES2018" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */,
"module": "commonjs" /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */,
"lib": ["es2015"] /* Specify library files to be included in the compilation. */,
// "allowJs": true, /* Allow javascript files to be compiled. */
// "checkJs": true, /* Report errors in .js files. */
// "jsx": "preserve", /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
// "declaration": true, /* Generates corresponding '.d.ts' file. */
// "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
// "outDir": "./", /* Redirect output structure to the directory. */
// "rootDir": "./", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "composite": true, /* Enable project compilation */
// "removeComments": true, /* Do not emit comments to output. */
// "noEmit": true, /* Do not emit outputs. */
// "importHelpers": true, /* Import emit helpers from 'tslib'. */
// "downlevelIteration": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
// "isolatedModules": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
/* Strict Type-Checking Options */
"strict": true /* Enable all strict type-checking options. */,
// "noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* Enable strict null checks. */
// "strictFunctionTypes": true, /* Enable strict checking of function types. */
// "strictPropertyInitialization": true, /* Enable strict checking of property initialization in classes. */
// "noImplicitThis": true, /* Raise error on 'this' expressions with an implied 'any' type. */
// "alwaysStrict": true, /* Parse in strict mode and emit "use strict" for each source file. */
/* Additional Checks */
// "noUnusedLocals": true, /* Report errors on unused locals. */
// "noUnusedParameters": true, /* Report errors on unused parameters. */
// "noImplicitReturns": true, /* Report error when not all code paths in function return a value. */
// "noFallthroughCasesInSwitch": true, /* Report errors for fallthrough cases in switch statement. */
/* Module Resolution Options */
// "moduleResolution": "node", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
// "baseUrl": "./", /* Base directory to resolve non-absolute module names. */
// "paths": {}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
// "rootDirs": [], /* List of root folders whose combined content represents the structure of the project at runtime. */
// "typeRoots": [], /* List of folders to include type definitions from. */
// "types": [], /* Type declaration files to be included in compilation. */
// "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
"esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
/* Source Map Options */
// "sourceRoot": "", /* Specify the location where debugger should locate TypeScript files instead of source locations. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Emit a single file with source maps instead of having a separate file. */
// "inlineSources": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
/* Experimental Options */
// "experimentalDecorators": true, /* Enables experimental support for ES7 decorators. */
// "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
}
}
Just add ES2018 to lib in tsconfig.json:
"lib": [
"ES2018"
]
lib is different to target. target roughly means the JavaScript version of the generated output files. lib means the features you will use in TypeScript. For example, you can use new features in ES2018 ("lib": ["ES2018"]), but still target at ES6 ("target": "ES6"). Those new features will be translated to ES6 during compilation (this may be done via third party tools like babel, and some new features may not be translatable, but these are just implementation details).

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