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I am trying to write a server in NodeJs using Typescript. I have installed these devDependencies:

    "@types/config": "^0.0.38",
    "@types/express": "^4.17.12",
    "@types/jsonwebtoken": "^8.5.1",
    "@types/lodash": "^4.14.170",
    "@types/morgan": "^1.9.2",   

    "nodemon": "^2.0.7",
    "tslint": "^6.1.3",
    "typescript": "^4.3.2"

My tsconfig.json is something like this:

{
  "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": "./dist/",                              /* Redirect output structure to the directory. */
    "rootDir": "./src",                          /* 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": "./src",                             /* 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. */
  },
  "include": [ "src/**/*"],
  "exclude": [ "node_modules" ]
}

My project directory structure is somethig like this:

src
 -> app
    -> bootstrap
    -> api
    -> models
    -> ..... more directories
    -> server.ts

dist
 ->app //generated files in .js
    -> boostrap
    -> api
    -> ..... more directories
    -> server.js    

My server.ts file has following absolute working imports:

import express from 'express';

import bootstrap from 'app/bootstrap'

import logger from 'app/services/logger';

const port = process.env.PORT || 8200;

const app = express();

bootstrap(app).then(mongo=>{
  app.listen({ port }, () => logger.info(`Server is listening on ${port}`));
}).catch(error=>{
  logger.error(error);
  process.exit(1);
});

The problem is when these .ts files are compiled and .js files are generated. and I run the application inside dist/app/server.js, I get cannot find module error, which node js throws due to my absolute path imports. Please help me fix this.

This is generated server.js file:

"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
var express_1 = __importDefault(require("express"));
var bootstrap_1 = __importDefault(require("app/bootstrap"));
var logger_1 = __importDefault(require("app/services/logger"));
var port = process.env.PORT || 8200;
var app = express_1.default();
bootstrap_1.default(app).then(function (mongo) {
    app.listen({ port: port }, function () { return logger_1.default.info("Server is listening on " + port); });
}).catch(function (error) {
    logger_1.default.error(error);
    process.exit(1);
});
//# sourceMappingURL=server.js.map

Here require("app/bootstrap") and require("app/services/logger") are producing error.

bhawanishiv
  • 345
  • 3
  • 8

2 Answers2

9

Your absolute imports are accepted by TypeScript compiler because in the tsconfig.json you specified baseUrl to "./src", which means paths are interpreted as relative to src directory.

However, NodeJS produces errors because it doesn't resolve imports in the same way. Absolute imports are expected to come from some node_modules folder. It accepts require("./bootstrap"), not require("app/bootstrap").

I suggest that you either disable baseUrl and migrate to relative imports, which is well supported by NodeJS; or, you can use a package bundler to transform the imports.

Wang Weixuan
  • 341
  • 2
  • 5
-1

maybe you could try paths

{
  "compilerOptions": {
    "baseUrl": "src",
    "paths": {
        "app/*": ["app/*"]
    },
}

but I prefer relative url personally

acfasj
  • 76
  • 7
  • That did not work @acfasj. I think I should use babel or something but don't know how. – bhawanishiv Jun 15 '21 at 18:13
  • something like [webpack alias](https://webpack.js.org/configuration/resolve/) ?, but you need to add webpack or other building tools... maybe you could search something like webpack alias – acfasj Jun 16 '21 at 04:04
  • 3
    Relative imports are a bad practice. – Michal Sep 21 '21 at 13:00
  • I prefer relative imports too, but absolute imports it‘s good way in some legacy codebase – acfasj Sep 23 '21 at 09:01